Merge remote-tracking branch 'upstream/3.1-stable' into dev

Signed-off-by: Florian Pritz <bluewind@xinu.at>

35 files changed, 630 insertions, 103 deletions

diff --git a/.gitattributes b/.gitattributes
index a4296d591..b4f0b6cbb 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -18,8 +18,6 @@ readme.rst
 tests/codeigniter/ export-ignore
 tests/travis/ export-ignore
 
-# User Guide Source Files
-user_guide_src
-
-# User Guide Compiled Files
+# User Guide source files and compiled files
+user_guide_src export-ignore
 user_guide export-ignore
diff --git a/.github/workflows/test-phpunit.yml b/.github/workflows/test-phpunit.yml
new file mode 100644
index 000000000..3468dfdfb
--- /dev/null
+++ b/.github/workflows/test-phpunit.yml
@@ -0,0 +1,119 @@
+name: PHPUnit
+
+on: [push, pull_request]
+
+jobs:
+  tests:
+    runs-on: ubuntu-18.04
+    if: "!contains(github.event.head_commit.message, '[ci skip]')"
+    env:
+      PHP_INI_VALUES: assert.exception=1, zend.assertions=1
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php: [ '8.1', '8.0', '7.4', '7.3', '7.2', '7.1', '7.0', '5.6', '5.5', '5.4' ]
+        DB: [ 'pdo/mysql', 'pdo/pgsql', 'pdo/sqlite', 'mysqli', 'pgsql', 'sqlite' ]
+        compiler: [ default ]
+        include:
+          - php: '8.1'
+            DB: 'pdo/mysql'
+            compiler: jit
+          - php: '8.1'
+            DB: 'pdo/pgsql'
+            compiler: jit
+          - php: '8.1'
+            DB: 'pdo/sqlite'
+            compiler: jit
+          - php: '8.1'
+            DB: 'mysqli'
+            compiler: jit
+          - php: '8.1'
+            DB: 'pgsql'
+            compiler: jit
+          - php: '8.1'
+            DB: 'sqlite'
+            compiler: jit
+          - php: '8.0'
+            DB: 'pdo/mysql'
+            compiler: jit
+          - php: '8.0'
+            DB: 'pdo/pgsql'
+            compiler: jit
+          - php: '8.0'
+            DB: 'pdo/sqlite'
+            compiler: jit
+          - php: '8.0'
+            DB: 'mysqli'
+            compiler: jit
+          - php: '8.0'
+            DB: 'pgsql'
+            compiler: jit
+          - php: '8.0'
+            DB: 'sqlite'
+            compiler: jit
+          - php: '5.6'
+            DB: 'mysql'
+            compiler: default
+          - php: '5.5'
+            DB: 'mysql'
+            compiler: default
+          - php: '5.4'
+            DB: 'mysql'
+            compiler: default
+
+    services:
+      postgres:
+        image: postgres:12
+        env:
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_DB: ci_test
+        ports:
+          - 5432:5432
+        options: --health-cmd=pg_isready --health-interval=10s --health-timeout=5s --health-retries=3
+
+      mysql:
+        image: mysql:5.7
+        env:
+          MYSQL_ALLOW_EMPTY_PASSWORD: true
+          MYSQL_USER: travis
+          MYSQL_PASSWORD: travis
+          MYSQL_DATABASE: ci_test
+        ports:
+          - 3306:3306
+        options: --health-cmd="mysqladmin ping" --health-interval=10s --health-timeout=5s --health-retries=3
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Override PHP ini values for JIT compiler
+        if: matrix.compiler == 'jit'
+        run: echo "PHP_INI_VALUES::assert.exception=1, zend.assertions=1, opcache.enable=1, opcache.enable_cli=1, opcache.optimization_level=-1, opcache.jit=1255, opcache.jit_buffer_size=64M" >> $GITHUB_ENV 
+
+      - name: Install PHP${{ matrix.php }} - DB ${{ matrix.DB }}
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          tools: composer, pecl
+          extensions: imagick, sqlite3, pgsql, mysqli, pdo, pdo_mysql, pdo_pgsql, pdo_sqlite, mbstring
+          ini-values: ${{ env.PHP_INI_VALUES }}
+          coverage: xdebug
+
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+      - name: Cache composer dependencies
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-   
+      - name: Install composer dependencies
+        run: composer install --no-progress --prefer-dist --optimize-autoloader
+
+      - name: PHPUnit Test
+        run: |
+          php -d zend.enable_gc=0 -d date.timezone=UTC -d mbstring.func_overload=7 -d mbstring.internal_encoding=UTF-8 vendor/bin/phpunit --coverage-text --configuration tests/travis/${{ matrix.DB }}.phpunit.xml
+        env:
+          XDEBUG_MODE: coverage
diff --git a/.gitignore b/.gitignore
index 3ea68afd3..95eba43c1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,6 +25,7 @@ code-coverage-report.xml
 code-coverage-report/
 
 composer.lock
+tests/mocks/database/ci_test.sqlite
 
 user_guide_src/build/*
 user_guide_src/cilexer/build/*
diff --git a/application/config/config.php b/application/config/config.php
index ec15f6c2c..845e6b55c 100644
--- a/application/config/config.php
+++ b/application/config/config.php
@@ -13,9 +13,9 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 |
 | WARNING: You MUST set this value!
 |
-| If it is not set, then CodeIgniter will try guess the protocol and path
-| your installation, but due to security concerns the hostname will be set
-| to $_SERVER['SERVER_ADDR'] if available, or localhost otherwise.
+| If it is not set, then CodeIgniter will try to guess the protocol and
+| path to your installation, but due to security concerns the hostname will
+| be set to $_SERVER['SERVER_ADDR'] if available, or localhost otherwise.
 | The auto-detection mechanism exists only for convenience during
 | development and MUST NOT be used in production!
 |
@@ -345,6 +345,10 @@ $config['encryption_key'] = '';
 |
 |	The session cookie name, must contain only [0-9a-z_-] characters
 |
+| 'sess_samesite'
+|
+|	Session cookie SameSite attribute: Lax (default), Strict or None
+|
 | 'sess_expiration'
 |
 |	The number of SECONDS you want the session to last.
@@ -385,6 +389,7 @@ $config['encryption_key'] = '';
 */
 $config['sess_driver'] = 'database';
 $config['sess_cookie_name'] = 'ci_session';
+$config['sess_samesite'] = 'Lax';
 $config['sess_expiration'] = 7200;
 $config['sess_save_path'] = "ci_sessions";
 $config['sess_match_ip'] = FALSE;
@@ -401,6 +406,7 @@ $config['sess_regenerate_destroy'] = FALSE;
 | 'cookie_path'     = Typically will be a forward slash
 | 'cookie_secure'   = Cookie will only be set if a secure HTTPS connection exists.
 | 'cookie_httponly' = Cookie will only be accessible via HTTP(S) (no javascript)
+| 'cookie_samesite' = Cookie's samesite attribute (Lax, Strict or None)
 |
 | Note: These settings (with the exception of 'cookie_prefix' and
 |       'cookie_httponly') will also affect sessions.
@@ -411,6 +417,7 @@ $config['cookie_domain']	= '';
 $config['cookie_path']		= '/';
 $config['cookie_secure']	= FALSE;
 $config['cookie_httponly'] 	= FALSE;
+$config['cookie_samesite'] 	= 'Lax';
 
 /*
 |--------------------------------------------------------------------------
diff --git a/application/config/mimes.php b/application/config/mimes.php
index f5407ff89..b2e989fea 100644
--- a/application/config/mimes.php
+++ b/application/config/mimes.php
@@ -162,7 +162,7 @@ return array(
 	'cdr'	=>	array('application/cdr', 'application/coreldraw', 'application/x-cdr', 'application/x-coreldraw', 'image/cdr', 'image/x-cdr', 'zz-application/zz-winassoc-cdr'),
 	'wma'	=>	array('audio/x-ms-wma', 'video/x-ms-asf'),
 	'jar'	=>	array('application/java-archive', 'application/x-java-application', 'application/x-jar', 'application/x-compressed'),
-	'svg'	=>	array('image/svg+xml', 'application/xml', 'text/xml'),
+	'svg'	=>	array('image/svg+xml', 'image/svg', 'application/xml', 'text/xml'),
 	'vcf'	=>	'text/x-vcard',
 	'srt'	=>	array('text/srt', 'text/plain'),
 	'vtt'	=>	array('text/vtt', 'text/plain'),
diff --git a/system/core/Common.php b/system/core/Common.php
index 9e23a4ea5..a9b8828e3 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -778,11 +778,9 @@ if ( ! function_exists('_stringify_attributes'))
 	 */
 	function _stringify_attributes($attributes, $js = FALSE)
 	{
-		$atts = NULL;
-
 		if (empty($attributes))
 		{
-			return $atts;
+			return NULL;
 		}
 
 		if (is_string($attributes))
@@ -792,6 +790,7 @@ if ( ! function_exists('_stringify_attributes'))
 
 		$attributes = (array) $attributes;
 
+		$atts = '';
 		foreach ($attributes as $key => $val)
 		{
 			$atts .= ($js) ? $key.'='.$val.',' : ' '.$key.'="'.$val.'"';
diff --git a/system/core/Input.php b/system/core/Input.php
index 3fb4121eb..47bdbfc5d 100644
--- a/system/core/Input.php
+++ b/system/core/Input.php
@@ -357,14 +357,15 @@ class CI_Input {
 	 * @param	string		$prefix		Cookie name prefix
 	 * @param	bool		$secure		Whether to only transfer cookies via SSL
 	 * @param	bool		$httponly	Whether to only makes the cookie accessible via HTTP (no javascript)
+	 * @param	string		$samesite	SameSite attribute
 	 * @return	void
 	 */
-	public function set_cookie($name, $value = '', $expire = '', $domain = '', $path = '/', $prefix = '', $secure = NULL, $httponly = NULL)
+	public function set_cookie($name, $value = '', $expire = '', $domain = '', $path = '/', $prefix = '', $secure = NULL, $httponly = NULL, $samesite = NULL)
 	{
 		if (is_array($name))
 		{
 			// always leave 'name' in last place, as the loop will break otherwise, due to $$item
-			foreach (array('value', 'expire', 'domain', 'path', 'prefix', 'secure', 'httponly', 'name') as $item)
+			foreach (array('value', 'expire', 'domain', 'path', 'prefix', 'secure', 'httponly', 'name', 'samesite') as $item)
 			{
 				if (isset($name[$item]))
 				{
@@ -405,7 +406,47 @@ class CI_Input {
 			$expire = ($expire > 0) ? time() + $expire : 0;
 		}
 
-		setcookie($prefix.$name, $value, $expire, $path, $domain, $secure, $httponly);
+		isset($samesite) OR $samesite = config_item('cookie_samesite');
+		if (isset($samesite))
+		{
+			$samesite = ucfirst(strtolower($samesite));
+			in_array($samesite, array('Lax', 'Strict', 'None'), TRUE) OR $samesite = 'Lax';
+		}
+		else
+		{
+			$samesite = 'Lax';
+		}
+
+		if ($samesite === 'None' && ! $secure)
+		{
+			log_message('error', $name.' cookie sent with SameSite=None, but without Secure attribute.');
+		}
+
+		if ( ! is_php('7.3'))
+		{
+			$maxage = $expire - time();
+			if ($maxage < 1)
+			{
+				$maxage = 0;
+			}
+
+			$cookie_header = 'Set-Cookie: '.$prefix.$name.'='.rawurlencode($value);
+			$cookie_header .= ($expire === 0 ? '' : '; Expires='.gmdate('D, d-M-Y H:i:s T', $expire)).'; Max-Age='.$maxage;
+			$cookie_header .= '; Path='.$path.($domain !== '' ? '; Domain='.$domain : '');
+			$cookie_header .= ($secure ? '; Secure' : '').($httponly ? '; HttpOnly' : '').'; SameSite='.$samesite;
+			header($cookie_header);
+			return;
+		}
+
+		$setcookie_options = array(
+			'expires' => $expire,
+			'path' => $path,
+			'domain' => $domain,
+			'secure' => $secure,
+			'httponly' => $httponly,
+			'samesite' => $samesite,
+		);
+		setcookie($prefix.$name, $value, $setcookie_options);
 	}
 
 	// --------------------------------------------------------------------
@@ -565,7 +606,7 @@ class CI_Input {
 				$which = FILTER_FLAG_IPV6;
 				break;
 			default:
-				$which = NULL;
+				$which = 0;
 				break;
 		}
 
diff --git a/system/core/Log.php b/system/core/Log.php
index f66f1aa48..683c16bac 100644
--- a/system/core/Log.php
+++ b/system/core/Log.php
@@ -122,7 +122,7 @@ class CI_Log {
 	{
 		$config =& get_config();
 
-		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		isset(self::$func_overload) OR self::$func_overload = ( ! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));
 
 		$this->_log_path = ($config['log_path'] !== '') ? $config['log_path'] : APPPATH.'logs/';
 		$this->_file_ext = (isset($config['log_file_extension']) && $config['log_file_extension'] !== '')
diff --git a/system/core/Output.php b/system/core/Output.php
index cef092600..8e3245b79 100644
--- a/system/core/Output.php
+++ b/system/core/Output.php
@@ -145,7 +145,7 @@ class CI_Output {
 			&& extension_loaded('zlib')
 		);
 
-		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		isset(self::$func_overload) OR self::$func_overload = ( ! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));
 
 		// Get mime types for later
 		$this->mimes =& get_mimes();
@@ -299,10 +299,14 @@ class CI_Output {
 	 */
 	public function get_header($header)
 	{
-		// Combine headers already sent with our batched headers
+		// We only need [x][0] from our multi-dimensional array
+		$header_lines = array_map(function ($headers)
+		{
+			return array_shift($headers);
+		}, $this->headers);
+
 		$headers = array_merge(
-			// We only need [x][0] from our multi-dimensional array
-			array_map('array_shift', $this->headers),
+			$header_lines,
 			headers_list()
 		);
 
diff --git a/system/core/Security.php b/system/core/Security.php
index e1dc2a92f..d1d4f8432 100644
--- a/system/core/Security.php
+++ b/system/core/Security.php
@@ -193,7 +193,7 @@ class CI_Security {
 			$this->_csrf_set_hash();
 		}
 
-		$this->charset = strtoupper(config_item('charset'));
+		$this->charset = strtoupper((string) config_item('charset'));
 
 		log_message('info', 'Security Class Initialized');
 	}
@@ -272,15 +272,35 @@ class CI_Security {
 			return FALSE;
 		}
 
-		setcookie(
-			$this->_csrf_cookie_name,
-			$this->_csrf_hash,
-			$expire,
-			config_item('cookie_path'),
-			config_item('cookie_domain'),
-			$secure_cookie,
-			config_item('cookie_httponly')
-		);
+		if (is_php('7.3'))
+		{
+			setcookie(
+				$this->_csrf_cookie_name,
+				$this->_csrf_hash,
+				array(
+					'expires'  => $expire,
+					'path'     => config_item('cookie_path'),
+					'domain'   => config_item('cookie_domain'),
+					'secure'   => $secure_cookie,
+					'httponly' => config_item('cookie_httponly'),
+					'samesite' => 'Strict'
+				)
+			);
+		}
+		else
+		{
+			$domain = trim(config_item('cookie_domain'));
+			header('Set-Cookie: '.$this->_csrf_cookie_name.'='.$this->_csrf_hash
+					.'; Expires='.gmdate('D, d-M-Y H:i:s T', $expire)
+					.'; Max-Age='.$this->_csrf_expire
+					.'; Path='.rawurlencode(config_item('cookie_path'))
+					.($domain === '' ? '' : '; Domain='.$domain)
+					.($secure_cookie ? '; Secure' : '')
+					.(config_item('cookie_httponly') ? '; HttpOnly' : '')
+					.'; SameSite=Strict'
+			);
+		}
+
 		log_message('info', 'CSRF cookie sent');
 
 		return $this;
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index c7bca96d8..fd7cd5543 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -887,7 +887,7 @@ abstract class CI_DB_driver {
 	{
 		return $this->_trans_status;
 	}
-	
+
 	// --------------------------------------------------------------------
 
 	/**
@@ -1576,6 +1576,7 @@ abstract class CI_DB_driver {
 				'\s+EXISTS\s*\(.*\)',        // EXISTS(sql)
 				'\s+NOT EXISTS\s*\(.*\)',    // NOT EXISTS(sql)
 				'\s+BETWEEN\s+',                 // BETWEEN value AND value
+				'\s+NOT BETWEEN\s+',             // NOT BETWEEN value AND value
 				'\s+IN\s*\(.*\)',            // IN(list)
 				'\s+NOT IN\s*\(.*\)',        // NOT IN (list)
 				'\s+LIKE\s+\S.*('.$_les.')?',    // LIKE 'expr'[ ESCAPE '%s']
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index c16897632..3dea1dbc5 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -116,6 +116,13 @@ class CI_DB_mysqli_driver extends CI_DB {
 	 */
 	public function db_connect($persistent = FALSE)
 	{
+		// PHP 8.1 changes default error handling mode from silent to exceptions - reverse that
+		if (is_php('8.1'))
+		{
+			$mysqli_driver = new mysqli_driver();
+			$mysqli_driver->report_mode = MYSQLI_REPORT_OFF;
+		}
+
 		// Do we have a socket path?
 		if ($this->hostname[0] === '/')
 		{
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index a9d75ebf2..511ef0e64 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -682,6 +682,16 @@ class CI_DB_oci8_driver extends CI_DB {
 	 */
 	protected function _close()
 	{
+		if (is_resource($this->curs_id))
+		{
+			oci_free_statement($this->curs_id);
+		}
+
+		if (is_resource($this->stmt_id))
+		{
+			oci_free_statement($this->stmt_id);
+		}
+
 		oci_close($this->conn_id);
 	}
 
diff --git a/system/database/drivers/pdo/pdo_driver.php b/system/database/drivers/pdo/pdo_driver.php
index d0a2bf959..b2178b684 100644
--- a/system/database/drivers/pdo/pdo_driver.php
+++ b/system/database/drivers/pdo/pdo_driver.php
@@ -131,6 +131,14 @@ class CI_DB_pdo_driver extends CI_DB {
 			$this->options[PDO::ATTR_PERSISTENT] = TRUE;
 		}
 
+		// From PHP8.0, default PDO::ATTR_ERRMODE is changed
+		// from PDO::ERRMODE_SILENT to PDO::ERRMODE_EXCEPTION
+		// as https://wiki.php.net/rfc/pdo_default_errmode
+		if ( ! isset($this->options[PDO::ATTR_ERRMODE]))
+		{
+			$this->options[PDO::ATTR_ERRMODE] = PDO::ERRMODE_SILENT;
+		}
+
 		try
 		{
 			return new PDO($this->dsn, $this->username, $this->password, $this->options);
diff --git a/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php b/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php
index 187cb2d09..4c3a5aaea 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php
@@ -54,6 +54,13 @@ class CI_DB_pdo_pgsql_forge extends CI_DB_pdo_forge {
 	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
 
 	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';
+
+	/**
 	 * UNSIGNED support
 	 *
 	 * @var	array
diff --git a/system/database/drivers/postgre/postgre_driver.php b/system/database/drivers/postgre/postgre_driver.php
index 84717d8b5..eb11a556a 100644
--- a/system/database/drivers/postgre/postgre_driver.php
+++ b/system/database/drivers/postgre/postgre_driver.php
@@ -135,7 +135,7 @@ class CI_DB_postgre_driver extends CI_DB {
 	 * Database connection
 	 *
 	 * @param	bool	$persistent
-	 * @return	resource
+	 * @return	resource|object
 	 */
 	public function db_connect($persistent = FALSE)
 	{
@@ -226,7 +226,7 @@ class CI_DB_postgre_driver extends CI_DB {
 	 * Execute the query
 	 *
 	 * @param	string	$sql	an SQL query
-	 * @return	resource
+	 * @return	resource|object
 	 */
 	protected function _execute($sql)
 	{
diff --git a/system/database/drivers/postgre/postgre_result.php b/system/database/drivers/postgre/postgre_result.php
index a0a628f0a..d977a60e3 100644
--- a/system/database/drivers/postgre/postgre_result.php
+++ b/system/database/drivers/postgre/postgre_result.php
@@ -126,7 +126,7 @@ class CI_DB_postgre_result extends CI_DB_result {
 	 */
 	public function free_result()
 	{
-		if (is_resource($this->result_id))
+		if ($this->result_id !== FALSE)
 		{
 			pg_free_result($this->result_id);
 			$this->result_id = FALSE;
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index dcc4ca0d3..6c453da3f 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -397,7 +397,7 @@ class CI_Email {
 		$this->initialize($config);
 		$this->_safe_mode = ( ! is_php('5.4') && ini_get('safe_mode'));
 
-		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		isset(self::$func_overload) OR self::$func_overload = ( ! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));
 
 		log_message('info', 'Email Class Initialized');
 	}
diff --git a/system/libraries/Encryption.php b/system/libraries/Encryption.php
index cb8ad9de9..933f6f232 100644
--- a/system/libraries/Encryption.php
+++ b/system/libraries/Encryption.php
@@ -161,7 +161,7 @@ class CI_Encryption {
 			show_error('Encryption: Unable to find an available encryption driver.');
 		}
 
-		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		isset(self::$func_overload) OR self::$func_overload = ( ! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));
 		$this->initialize($params);
 
 		if ( ! isset($this->_key) && self::strlen($key = config_item('encryption_key')) > 0)
@@ -476,7 +476,7 @@ class CI_Encryption {
 
 		$iv = ($iv_size = openssl_cipher_iv_length($params['handle']))
 			? $this->create_key($iv_size)
-			: NULL;
+			: '';
 
 		$data = openssl_encrypt(
 			$data,
@@ -585,7 +585,7 @@ class CI_Encryption {
 		}
 		else
 		{
-			$iv = NULL;
+			$iv = '';
 		}
 
 		if (mcrypt_generic_init($params['handle'], $params['key'], $iv) < 0)
@@ -632,7 +632,7 @@ class CI_Encryption {
 		}
 		else
 		{
-			$iv = NULL;
+			$iv = '';
 		}
 
 		return empty($params['handle'])
@@ -910,8 +910,8 @@ class CI_Encryption {
 	protected static function strlen($str)
 	{
 		return (self::$func_overload)
-			? mb_strlen($str, '8bit')
-			: strlen($str);
+			? mb_strlen((string) $str, '8bit')
+			: strlen((string) $str);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 9d976984e..1b7bbb96c 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -1056,7 +1056,7 @@ class CI_Form_validation {
 	{
 		return is_array($str)
 			? (empty($str) === FALSE)
-			: (trim($str) !== '');
+			: (trim((string) $str) !== '');
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/libraries/Ftp.php b/system/libraries/Ftp.php
index 61fa80c0f..92644153a 100644
--- a/system/libraries/Ftp.php
+++ b/system/libraries/Ftp.php
@@ -202,7 +202,7 @@ class CI_FTP {
 	 */
 	protected function _is_conn()
 	{
-		if ( ! is_resource($this->conn_id))
+		if ($this->conn_id !== FALSE)
 		{
 			if ($this->debug === TRUE)
 			{
diff --git a/system/libraries/Session/CI_Session_driver_interface.php b/system/libraries/Session/CI_Session_driver_interface.php
new file mode 100644
index 000000000..a854e92af
--- /dev/null
+++ b/system/libraries/Session/CI_Session_driver_interface.php
@@ -0,0 +1,58 @@
+<?php
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP
+ *
+ * This content is released under the MIT License (MIT)
+ *
+ * Copyright (c) 2022, CodeIgniter Foundation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @package	CodeIgniter
+ * @author	EllisLab Dev Team
+ * @copyright	Copyright (c) 2022, CodeIgniter Foundation (https://codeigniter.com/)
+ * @license	http://opensource.org/licenses/MIT	MIT License
+ * @link	https://codeigniter.com
+ * @since	Version 3.0.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * CI_Session_driver_interface
+ *
+ * A compatibility typeless SessionHandlerInterface alias
+ *
+ * @package	CodeIgniter
+ * @subpackage	Libraries
+ * @category	Sessions
+ * @author	Andrey Andreev
+ * @link	https://codeigniter.com/userguide3/libraries/sessions.html
+ */
+interface CI_Session_driver_interface {
+
+	public function open($save_path, $name);
+	public function close();
+	public function read($session_id);
+	public function write($session_id, $session_data);
+	public function destroy($session_id);
+	public function gc($maxlifetime);
+}
diff --git a/system/libraries/Session/OldSessionWrapper.php b/system/libraries/Session/OldSessionWrapper.php
new file mode 100644
index 000000000..a8bc1d0c0
--- /dev/null
+++ b/system/libraries/Session/OldSessionWrapper.php
@@ -0,0 +1,88 @@
+<?php
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP
+ *
+ * This content is released under the MIT License (MIT)
+ *
+ * Copyright (c) 2022, CodeIgniter Foundation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @package	CodeIgniter
+ * @author	EllisLab Dev Team
+ * @copyright	Copyright (c) 2022, CodeIgniter Foundation (https://codeigniter.com/)
+ * @license	http://opensource.org/licenses/MIT	MIT License
+ * @link	https://codeigniter.com
+ * @since	Version 3.0.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * OldSessionWrapper
+ *
+ * PHP 8 Session handler compatibility wrapper, pre-PHP8 version
+ *
+ * @package	CodeIgniter
+ * @subpackage	Libraries
+ * @category	Sessions
+ * @author	Andrey Andreev
+ * @link	https://codeigniter.com/userguide3/libraries/sessions.html
+ */
+class CI_SessionWrapper implements SessionHandlerInterface {
+
+	protected $driver;
+
+	public function __construct(CI_Session_driver_interface $driver)
+	{
+		$this->driver = $driver;
+	}
+
+	public function open($save_path, $name)
+	{
+		return $this->driver->open($save_path, $name);
+	}
+
+	public function close()
+	{
+		return $this->driver->close();
+	}
+
+	public function read($id)
+	{
+		return $this->driver->read($id);
+	}
+
+	public function write($id, $data)
+	{
+		return $this->driver->write($id, $data);
+	}
+
+	public function destroy($id)
+	{
+		return $this->driver->destroy($id);
+	}
+
+	public function gc($maxlifetime)
+	{
+		return $this->driver->gc($maxlifetime);
+	}
+}
diff --git a/system/libraries/Session/PHP8SessionWrapper.php b/system/libraries/Session/PHP8SessionWrapper.php
new file mode 100644
index 000000000..c6dfaf7e0
--- /dev/null
+++ b/system/libraries/Session/PHP8SessionWrapper.php
@@ -0,0 +1,90 @@
+<?php
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP
+ *
+ * This content is released under the MIT License (MIT)
+ *
+ * Copyright (c) 2022, CodeIgniter Foundation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @package	CodeIgniter
+ * @author	EllisLab Dev Team
+ * @copyright	Copyright (c) 2022, CodeIgniter Foundation (https://codeigniter.com/)
+ * @license	http://opensource.org/licenses/MIT	MIT License
+ * @link	https://codeigniter.com
+ * @since	Version 3.0.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PHP8SessionWrapper
+ *
+ * PHP 8 Session handler compatibility wrapper
+ *
+ * @package	CodeIgniter
+ * @subpackage	Libraries
+ * @category	Sessions
+ * @author	Andrey Andreev
+ * @link	https://codeigniter.com/userguide3/libraries/sessions.html
+ */
+class CI_SessionWrapper implements SessionHandlerInterface {
+
+	protected CI_Session_driver_interface $driver;
+
+	public function __construct(CI_Session_driver_interface $driver)
+	{
+		$this->driver = $driver;
+	}
+
+	public function open(string $save_path, string $name): bool
+	{
+		return $this->driver->open($save_path, $name);
+	}
+
+	public function close(): bool
+	{
+		return $this->driver->close();
+	}
+
+	#[\ReturnTypeWillChange]
+	public function read(string $id): mixed
+	{
+		return $this->driver->read($id);
+	}
+
+	public function write(string $id, string $data): bool
+	{
+		return $this->driver->write($id, $data);
+	}
+
+	public function destroy(string $id): bool
+	{
+		return $this->driver->destroy($id);
+	}
+
+	#[\ReturnTypeWillChange]
+	public function gc(int $maxlifetime): mixed
+	{
+		return $this->driver->gc($maxlifetime);
+	}
+}
diff --git a/system/libraries/Session/Session.php b/system/libraries/Session/Session.php
index 06b953ab2..8d3ba2857 100644
--- a/system/libraries/Session/Session.php
+++ b/system/libraries/Session/Session.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
  * @license	https://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 2.0.0
@@ -102,31 +103,24 @@ class CI_Session {
 		$this->_configure($params);
 		$this->_config['_sid_regexp'] = $this->_sid_regexp;
 
-		$class = new $class($this->_config);
-		if ($class instanceof SessionHandlerInterface)
+		$class   = new $class($this->_config);
+		$wrapper = new CI_SessionWrapper($class);
+		if (is_php('5.4'))
 		{
-			if (is_php('5.4'))
-			{
-				session_set_save_handler($class, TRUE);
-			}
-			else
-			{
-				session_set_save_handler(
-					array($class, 'open'),
-					array($class, 'close'),
-					array($class, 'read'),
-					array($class, 'write'),
-					array($class, 'destroy'),
-					array($class, 'gc')
-				);
-
-				register_shutdown_function('session_write_close');
-			}
+			session_set_save_handler($wrapper, TRUE);
 		}
 		else
 		{
-			log_message('error', "Session: Driver '".$this->_driver."' doesn't implement SessionHandlerInterface. Aborting.");
-			return;
+			session_set_save_handler(
+				array($wrapper, 'open'),
+				array($wrapper, 'close'),
+				array($wrapper, 'read'),
+				array($wrapper, 'write'),
+				array($wrapper, 'destroy'),
+				array($wrapper, 'gc')
+			);
+
+			register_shutdown_function('session_write_close');
 		}
 
 		// Sanitize the cookie, because apparently PHP doesn't do that for userspace handlers
@@ -160,15 +154,36 @@ class CI_Session {
 		// unless it is being currently created or regenerated
 		elseif (isset($_COOKIE[$this->_config['cookie_name']]) && $_COOKIE[$this->_config['cookie_name']] === session_id())
 		{
-			setcookie(
-				$this->_config['cookie_name'],
-				session_id(),
-				(empty($this->_config['cookie_lifetime']) ? 0 : time() + $this->_config['cookie_lifetime']),
-				$this->_config['cookie_path'],
-				$this->_config['cookie_domain'],
-				$this->_config['cookie_secure'],
-				TRUE
-			);
+			$expires = empty($this->_config['cookie_lifetime']) ? 0 : time() + $this->_config['cookie_lifetime'];
+			if (is_php('7.3'))
+			{
+				setcookie(
+					$this->_config['cookie_name'],
+					session_id(),
+					array(
+						'expires' => $expires,
+						'path' => $this->_config['cookie_path'],
+						'domain' => $this->_config['cookie_domain'],
+						'secure' => $this->_config['cookie_secure'],
+						'httponly' => TRUE,
+						'samesite' => $this->_config['cookie_samesite']
+					)
+				);
+			}
+			else
+			{
+				$header = 'Set-Cookie: '.$this->_config['cookie_name'].'='.session_id();
+				$header .= empty($expires) ? '' : '; Expires='.gmdate('D, d-M-Y H:i:s T', $expires).'; Max-Age='.$this->_config['cookie_lifetime'];
+				$header .= '; Path='.$this->_config['cookie_path'];
+				$header .= ($this->_config['cookie_domain'] !== '' ? '; Domain='.$this->_config['cookie_domain'] : '');
+				$header .= ($this->_config['cookie_secure'] ? '; Secure' : '').'; HttpOnly; SameSite='.$this->_config['cookie_samesite'];
+				header($header);
+			}
+
+			if ( ! $this->_config['cookie_secure'] && $this->_config['cookie_samesite'] === 'None')
+			{
+				log_message('error', 'Session:', $this->_config['cookie_name'].' cookie sent with SameSite=None, but without Secure attribute.');
+			}
 		}
 
 		$this->_ci_init_vars();
@@ -193,6 +208,10 @@ class CI_Session {
 		// PHP 5.4 compatibility
 		interface_exists('SessionHandlerInterface', FALSE) OR require_once(BASEPATH.'libraries/Session/SessionHandlerInterface.php');
 
+		require_once(BASEPATH.'libraries/Session/CI_Session_driver_interface.php');
+		$wrapper = is_php('8.0') ? 'PHP8SessionWrapper' : 'OldSessionWrapper';
+		require_once(BASEPATH.'libraries/Session/'.$wrapper.'.php');
+
 		$prefix = config_item('subclass_prefix');
 
 		if ( ! class_exists('CI_Session_driver', FALSE))
@@ -286,13 +305,43 @@ class CI_Session {
 		isset($params['cookie_domain']) OR $params['cookie_domain'] = config_item('cookie_domain');
 		isset($params['cookie_secure']) OR $params['cookie_secure'] = (bool) config_item('cookie_secure');
 
-		session_set_cookie_params(
-			$params['cookie_lifetime'],
-			$params['cookie_path'],
-			$params['cookie_domain'],
-			$params['cookie_secure'],
-			TRUE // HttpOnly; Yes, this is intentional and not configurable for security reasons
-		);
+		isset($params['cookie_samesite']) OR $params['cookie_samesite'] = config_item('sess_samesite');
+		if ( ! isset($params['cookie_samesite']) && is_php('7.3'))
+		{
+			$params['cookie_samesite'] = ini_get('session.cookie_samesite');
+		}
+
+		if (isset($params['cookie_samesite']))
+		{
+			$params['cookie_samesite'] = ucfirst(strtolower($params['cookie_samesite']));
+			in_array($params['cookie_samesite'], array('Lax', 'Strict', 'None'), TRUE) OR $params['cookie_samesite'] = 'Lax';
+		}
+		else
+		{
+			$params['cookie_samesite'] = 'Lax';
+		}
+
+		if (is_php('7.3'))
+		{
+			session_set_cookie_params(array(
+				'lifetime' => $params['cookie_lifetime'],
+				'path'     => $params['cookie_path'],
+				'domain'   => $params['cookie_domain'],
+				'secure'   => $params['cookie_secure'],
+				'httponly' => TRUE,
+				'samesite' => $params['cookie_samesite']
+			));
+		}
+		else
+		{
+			session_set_cookie_params(
+				$params['cookie_lifetime'],
+				$params['cookie_path'].'; SameSite='.$params['cookie_samesite'],
+				$params['cookie_domain'],
+				$params['cookie_secure'],
+				TRUE // HttpOnly; Yes, this is intentional and not configurable for security reasons
+			);
+		}
 
 		if (empty($expiration))
 		{
@@ -723,7 +772,7 @@ class CI_Session {
 	 *
 	 * Legacy CI_Session compatibility method
 	 *
-	 * @returns	array
+	 * @return	array
 	 */
 	public function &get_userdata()
 	{
diff --git a/system/libraries/Session/SessionHandlerInterface.php b/system/libraries/Session/SessionHandlerInterface.php
index 95d2488b4..914eae03f 100644
--- a/system/libraries/Session/SessionHandlerInterface.php
+++ b/system/libraries/Session/SessionHandlerInterface.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (http://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (http://codeigniter.com/)
  * @license	http://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 3.0.0
diff --git a/system/libraries/Session/Session_driver.php b/system/libraries/Session/Session_driver.php
index 734b6e052..b1b1b073e 100644
--- a/system/libraries/Session/Session_driver.php
+++ b/system/libraries/Session/Session_driver.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
  * @license	https://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 3.0.0
@@ -46,7 +47,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
  * @author	Andrey Andreev
  * @link	https://codeigniter.com/userguide3/libraries/sessions.html
  */
-abstract class CI_Session_driver implements SessionHandlerInterface {
+abstract class CI_Session_driver {
 
 	protected $_config;
 
@@ -139,14 +140,28 @@ abstract class CI_Session_driver implements SessionHandlerInterface {
 	 */
 	protected function _cookie_destroy()
 	{
+		if ( ! is_php('7.3'))
+		{
+			$header = 'Set-Cookie: '.$this->_config['cookie_name'].'=';
+			$header .= '; Expires='.gmdate('D, d-M-Y H:i:s T', 1).'; Max-Age=-1';
+			$header .= '; Path='.$this->_config['cookie_path'];
+			$header .= ($this->_config['cookie_domain'] !== '' ? '; Domain='.$this->_config['cookie_domain'] : '');
+			$header .= ($this->_config['cookie_secure'] ? '; Secure' : '').'; HttpOnly; SameSite='.$this->_config['cookie_samesite'];
+			header($header);
+			return;
+		}
+
 		return setcookie(
 			$this->_config['cookie_name'],
 			NULL,
-			1,
-			$this->_config['cookie_path'],
-			$this->_config['cookie_domain'],
-			$this->_config['cookie_secure'],
-			TRUE
+			array(
+				'expires' => 1,
+				'path' => $this->_config['cookie_path'],
+				'domain' => $this->_config['cookie_domain'],
+				'secure' => $this->_config['cookie_secure'],
+				'httponly' => TRUE,
+				'samesite' => $this->_config['cookie_samesite']
+			)
 		);
 	}
 
diff --git a/system/libraries/Session/drivers/Session_database_driver.php b/system/libraries/Session/drivers/Session_database_driver.php
index a3055af5e..2f788a1a1 100644
--- a/system/libraries/Session/drivers/Session_database_driver.php
+++ b/system/libraries/Session/drivers/Session_database_driver.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
  * @license	https://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 3.0.0
@@ -46,7 +47,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
  * @author	Andrey Andreev
  * @link	https://codeigniter.com/userguide3/libraries/sessions.html
  */
-class CI_Session_database_driver extends CI_Session_driver implements SessionHandlerInterface {
+class CI_Session_database_driver extends CI_Session_driver implements CI_Session_driver_interface {
 
 	/**
 	 * DB object
diff --git a/system/libraries/Session/drivers/Session_files_driver.php b/system/libraries/Session/drivers/Session_files_driver.php
index 49bf5b781..4b7b9878b 100644
--- a/system/libraries/Session/drivers/Session_files_driver.php
+++ b/system/libraries/Session/drivers/Session_files_driver.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
  * @license	https://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 3.0.0
@@ -46,7 +47,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
  * @author	Andrey Andreev
  * @link	https://codeigniter.com/userguide3/libraries/sessions.html
  */
-class CI_Session_files_driver extends CI_Session_driver implements SessionHandlerInterface {
+class CI_Session_files_driver extends CI_Session_driver implements CI_Session_driver_interface {
 
 	/**
 	 * Save path
@@ -115,7 +116,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 
 		$this->_sid_regexp = $this->_config['_sid_regexp'];
 
-		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		isset(self::$func_overload) OR self::$func_overload = ( ! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));
 	}
 
 	// ------------------------------------------------------------------------
diff --git a/system/libraries/Session/drivers/Session_memcached_driver.php b/system/libraries/Session/drivers/Session_memcached_driver.php
index b4d3eb464..d84a9df1d 100644
--- a/system/libraries/Session/drivers/Session_memcached_driver.php
+++ b/system/libraries/Session/drivers/Session_memcached_driver.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
  * @license	https://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 3.0.0
@@ -46,7 +47,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
  * @author	Andrey Andreev
  * @link	https://codeigniter.com/userguide3/libraries/sessions.html
  */
-class CI_Session_memcached_driver extends CI_Session_driver implements SessionHandlerInterface {
+class CI_Session_memcached_driver extends CI_Session_driver implements CI_Session_driver_interface {
 
 	/**
 	 * Memcached instance
diff --git a/system/libraries/Session/drivers/Session_redis_driver.php b/system/libraries/Session/drivers/Session_redis_driver.php
index d65c6ee14..b112a18c8 100644
--- a/system/libraries/Session/drivers/Session_redis_driver.php
+++ b/system/libraries/Session/drivers/Session_redis_driver.php
@@ -6,7 +6,7 @@
  *
  * This content is released under the MIT License (MIT)
  *
- * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
+ * Copyright (c) 2019 - 2022, CodeIgniter Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@
  * @author	EllisLab Dev Team
  * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
  * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
+ * @copyright	Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
  * @license	https://opensource.org/licenses/MIT	MIT License
  * @link	https://codeigniter.com
  * @since	Version 3.0.0
@@ -46,7 +47,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
  * @author	Andrey Andreev
  * @link	https://codeigniter.com/userguide3/libraries/sessions.html
  */
-class CI_Session_redis_driver extends CI_Session_driver implements SessionHandlerInterface {
+class CI_Session_redis_driver extends CI_Session_driver implements CI_Session_driver_interface {
 
 	/**
 	 * phpRedis instance
diff --git a/system/libraries/Upload.php b/system/libraries/Upload.php
index ae60f35af..e754205de 100644
--- a/system/libraries/Upload.php
+++ b/system/libraries/Upload.php
@@ -1227,7 +1227,7 @@ class CI_Upload {
 		if (function_exists('finfo_file'))
 		{
 			$finfo = @finfo_open(FILEINFO_MIME);
-			if (is_resource($finfo)) // It is possible that a FALSE value is returned, if there is no magic MIME database file found on the system
+			if ($finfo !== FALSE) // It is possible that a FALSE value is returned, if there is no magic MIME database file found on the system
 			{
 				$mime = @finfo_file($finfo, $file['tmp_name']);
 				finfo_close($finfo);
diff --git a/system/libraries/User_agent.php b/system/libraries/User_agent.php
index a42975b35..c144db7a8 100644
--- a/system/libraries/User_agent.php
+++ b/system/libraries/User_agent.php
@@ -498,7 +498,7 @@ class CI_User_agent {
 			else
 			{
 				$referer_host = @parse_url($_SERVER['HTTP_REFERER'], PHP_URL_HOST);
-				$own_host = parse_url(config_item('base_url'), PHP_URL_HOST);
+				$own_host = parse_url((string) config_item('base_url'), PHP_URL_HOST);
 
 				$this->referer = ($referer_host && $referer_host !== $own_host);
 			}
diff --git a/system/libraries/Xmlrpc.php b/system/libraries/Xmlrpc.php
index 32b236b43..d500bcf87 100644
--- a/system/libraries/Xmlrpc.php
+++ b/system/libraries/Xmlrpc.php
@@ -1914,7 +1914,7 @@ class XML_RPC_Values extends CI_Xmlrpc
 	*/
 	public function iso8601_encode($time, $utc = FALSE)
 	{
-		return ($utc) ? strftime('%Y%m%dT%H:%i:%s', $time) : gmstrftime('%Y%m%dT%H:%i:%s', $time);
+		return ($utc) ? date('Ymd\TH:i:s', $time) : gmdate('Ymd\TH:i:s', $time);
 	}
 
 } // END XML_RPC_Values Class
diff --git a/system/libraries/Zip.php b/system/libraries/Zip.php
index e99873ae7..44586697a 100644
--- a/system/libraries/Zip.php
+++ b/system/libraries/Zip.php
@@ -119,7 +119,7 @@ class CI_Zip {
 	 */
 	public function __construct()
 	{
-		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		isset(self::$func_overload) OR self::$func_overload = ( ! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));
 
 		$this->now = time();
 		log_message('info', 'Zip Compression Class Initialized');