Merge branch '3.1-stable' into develop

Resolved conflicts:
	system/core/CodeIgniter.php
	user_guide_src/source/changelog.rst
	user_guide_src/source/conf.py
	user_guide_src/source/installation/downloads.rst
	user_guide_src/source/installation/upgrading.rst
	user_guide_src/source/libraries/form_validation.rst

27 files changed, 550 insertions, 107 deletions

diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index e6ce13d81..66ed9ec8f 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -55,7 +55,7 @@ defined('BASEPATH') OR exit('No direct script access allowed');
  * @var	string
  *
  */
-	define('CI_VERSION', '3.2.0-dev');
+	const CI_VERSION = '3.2.0-dev';
 
 /*
  * ------------------------------------------------------
@@ -416,10 +416,29 @@ if ( ! is_php('5.4'))
 			$params = array($method, array_slice($URI->rsegments, 2));
 			$method = '_remap';
 		}
-		elseif ( ! is_callable(array($class, $method)))
+		elseif ( ! method_exists($class, $method))
 		{
 			$e404 = TRUE;
 		}
+		/**
+		 * DO NOT CHANGE THIS, NOTHING ELSE WORKS!
+		 *
+		 * - method_exists() returns true for non-public methods, which passes the previous elseif
+		 * - is_callable() returns false for PHP 4-style constructors, even if there's a __construct()
+		 * - method_exists($class, '__construct') won't work because CI_Controller::__construct() is inherited
+		 * - People will only complain if this doesn't work, even though it is documented that it shouldn't.
+		 *
+		 * ReflectionMethod::isConstructor() is the ONLY reliable check,
+		 * knowing which method will be executed as a constructor.
+		 */
+		elseif ( ! is_callable(array($class, $method)) && strcasecmp($class, $method) === 0)
+		{
+			$reflection = new ReflectionMethod($class, $method);
+			if ( ! $reflection->isPublic() OR $reflection->isConstructor())
+			{
+				$e404 = TRUE;
+			}
+		}
 	}
 
 	if ($e404)
diff --git a/system/core/Common.php b/system/core/Common.php
index 2c7651943..91c585f7d 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -544,13 +544,18 @@ if ( ! function_exists('set_status_header'))
 				416	=> 'Requested Range Not Satisfiable',
 				417	=> 'Expectation Failed',
 				422	=> 'Unprocessable Entity',
+				426	=> 'Upgrade Required',
+				428	=> 'Precondition Required',
+				429	=> 'Too Many Requests',
+				431	=> 'Request Header Fields Too Large',
 
 				500	=> 'Internal Server Error',
 				501	=> 'Not Implemented',
 				502	=> 'Bad Gateway',
 				503	=> 'Service Unavailable',
 				504	=> 'Gateway Timeout',
-				505	=> 'HTTP Version Not Supported'
+				505	=> 'HTTP Version Not Supported',
+				511	=> 'Network Authentication Required',
 			);
 
 			if (isset($stati[$code]))
@@ -656,6 +661,7 @@ if ( ! function_exists('_exception_handler'))
 		$_error =& load_class('Exceptions', 'core');
 		$_error->log_exception('error', 'Exception: '.$exception->getMessage(), $exception->getFile(), $exception->getLine());
 
+		is_cli() OR set_status_header(500);
 		// Should we display the error?
 		if (str_ireplace(array('off', 'none', 'no', 'false', 'null'), '', ini_get('display_errors')))
 		{
diff --git a/system/core/Exceptions.php b/system/core/Exceptions.php
index a1c6a1970..4e10f2831 100644
--- a/system/core/Exceptions.php
+++ b/system/core/Exceptions.php
@@ -207,7 +207,6 @@ class CI_Exceptions {
 		}
 		else
 		{
-			set_status_header(500);
 			$templates_path .= 'html'.DIRECTORY_SEPARATOR;
 		}
 
diff --git a/system/core/Log.php b/system/core/Log.php
index 986121526..cf6c75a95 100644
--- a/system/core/Log.php
+++ b/system/core/Log.php
@@ -104,6 +104,13 @@ class CI_Log {
 	 */
 	protected $_levels = array('ERROR' => 1, 'DEBUG' => 2, 'INFO' => 3, 'ALL' => 4);
 
+	/**
+	 * mbstring.func_override flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_override;
+
 	// --------------------------------------------------------------------
 
 	/**
@@ -115,6 +122,8 @@ class CI_Log {
 	{
 		$config =& get_config();
 
+		isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));
+
 		$this->_log_path = ($config['log_path'] !== '') ? $config['log_path'] : APPPATH.'logs/';
 		$this->_file_ext = (isset($config['log_file_extension']) && $config['log_file_extension'] !== '')
 			? ltrim($config['log_file_extension'], '.') : 'php';
@@ -208,9 +217,9 @@ class CI_Log {
 
 		$message .= $this->_format_line($level, $date, $msg);
 
-		for ($written = 0, $length = strlen($message); $written < $length; $written += $result)
+		for ($written = 0, $length = self::strlen($message); $written < $length; $written += $result)
 		{
-			if (($result = fwrite($fp, substr($message, $written))) === FALSE)
+			if (($result = fwrite($fp, self::substr($message, $written))) === FALSE)
 			{
 				break;
 			}
@@ -244,4 +253,44 @@ class CI_Log {
 	{
 		return $level.' - '.$date.' --> '.$message."\n";
 	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_override)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe substr()
+	 *
+	 * @param	string	$str
+	 * @param	int	$start
+	 * @param	int	$length
+	 * @return	string
+	 */
+	protected static function substr($str, $start, $length = NULL)
+	{
+		if (self::$func_override)
+		{
+			// mb_substr($str, $start, null, '8bit') returns an empty
+			// string on PHP 5.3
+			isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
+			return mb_substr($str, $start, $length, '8bit');
+		}
+
+		return isset($length)
+			? substr($str, $start, $length)
+			: substr($str, $start);
+	}
 }
diff --git a/system/core/Output.php b/system/core/Output.php
index 98db212a0..7921a54ef 100644
--- a/system/core/Output.php
+++ b/system/core/Output.php
@@ -123,6 +123,13 @@ class CI_Output {
 	public $parse_exec_vars = TRUE;
 
 	/**
+	 * mbstring.func_override flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_override;
+
+	/**
 	 * Class constructor
 	 *
 	 * Determines whether zLib output compression will be used.
@@ -138,6 +145,8 @@ class CI_Output {
 			&& extension_loaded('zlib')
 		);
 
+		isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));
+
 		// Get mime types for later
 		$this->mimes =& get_mimes();
 
@@ -304,9 +313,9 @@ class CI_Output {
 
 		for ($i = 0, $c = count($headers); $i < $c; $i++)
 		{
-			if (strncasecmp($header, $headers[$i], $l = strlen($header)) === 0)
+			if (strncasecmp($header, $headers[$i], $l = self::strlen($header)) === 0)
 			{
-				return trim(substr($headers[$i], $l+1));
+				return trim(self::substr($headers[$i], $l+1));
 			}
 		}
 
@@ -480,13 +489,13 @@ class CI_Output {
 				if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE)
 				{
 					header('Content-Encoding: gzip');
-					header('Content-Length: '.strlen($output));
+					header('Content-Length: '.self::strlen($output));
 				}
 				else
 				{
 					// User agent doesn't support gzip compression,
 					// so we'll have to decompress our cache
-					$output = gzinflate(substr($output, 10, -8));
+					$output = gzinflate(self::substr($output, 10, -8));
 				}
 			}
 
@@ -601,9 +610,9 @@ class CI_Output {
 
 			$output = $cache_info.'ENDCI--->'.$output;
 
-			for ($written = 0, $length = strlen($output); $written < $length; $written += $result)
+			for ($written = 0, $length = self::strlen($output); $written < $length; $written += $result)
 			{
-				if (($result = fwrite($fp, substr($output, $written))) === FALSE)
+				if (($result = fwrite($fp, self::substr($output, $written))) === FALSE)
 				{
 					break;
 				}
@@ -711,7 +720,7 @@ class CI_Output {
 		}
 
 		// Display the cache
-		$this->_display(substr($cache, strlen($match[0])));
+		$this->_display(self::substr($cache, self::strlen($match[0])));
 		log_message('debug', 'Cache file is current. Sending it to browser.');
 		return TRUE;
 	}
@@ -797,4 +806,43 @@ class CI_Output {
 		}
 	}
 
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_override)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe substr()
+	 *
+	 * @param	string	$str
+	 * @param	int	$start
+	 * @param	int	$length
+	 * @return	string
+	 */
+	protected static function substr($str, $start, $length = NULL)
+	{
+		if (self::$func_override)
+		{
+			// mb_substr($str, $start, null, '8bit') returns an empty
+			// string on PHP 5.3
+			isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
+			return mb_substr($str, $start, $length, '8bit');
+		}
+
+		return isset($length)
+			? substr($str, $start, $length)
+			: substr($str, $start);
+	}
 }
diff --git a/system/core/Security.php b/system/core/Security.php
index 3a5da4fde..d0308c5f9 100644
--- a/system/core/Security.php
+++ b/system/core/Security.php
@@ -133,15 +133,16 @@ class CI_Security {
 	 * @var	array
 	 */
 	protected $_never_allowed_str =	array(
-		'document.cookie'	=> '[removed]',
-		'document.write'	=> '[removed]',
-		'.parentNode'		=> '[removed]',
-		'.innerHTML'		=> '[removed]',
-		'-moz-binding'		=> '[removed]',
-		'<!--'				=> '&lt;!--',
-		'-->'				=> '--&gt;',
-		'<![CDATA['			=> '&lt;![CDATA[',
-		'<comment>'			=> '&lt;comment&gt;'
+		'document.cookie' => '[removed]',
+		'document.write'  => '[removed]',
+		'.parentNode'     => '[removed]',
+		'.innerHTML'      => '[removed]',
+		'-moz-binding'    => '[removed]',
+		'<!--'            => '&lt;!--',
+		'-->'             => '--&gt;',
+		'<![CDATA['       => '&lt;![CDATA[',
+		'<comment>'	  => '&lt;comment&gt;',
+		'<%'              => '&lt;&#37;'
 	);
 
 	/**
@@ -371,11 +372,17 @@ class CI_Security {
 		 *
 		 * Note: Use rawurldecode() so it does not remove plus signs
 		 */
-		do
+		if (stripos($str, '%') !== false)
 		{
-			$str = rawurldecode($str);
+			do
+			{
+				$oldstr = $str;
+				$str = rawurldecode($str);
+				$str = preg_replace_callback('#%(?:\s*[0-9a-f]){2,}#i', array($this, '_urldecodespaces'), $str);
+			}
+			while ($oldstr !== $str);
+			unset($oldstr);
 		}
-		while (preg_match('/%[0-9a-f]{2,}/i', $str));
 
 		/*
 		 * Convert character entities to ASCII
@@ -466,7 +473,7 @@ class CI_Security {
 
 			if (preg_match('/<a/i', $str))
 			{
-				$str = preg_replace_callback('#<a[^a-z0-9>]+([^>]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str);
+				$str = preg_replace_callback('#<a(?:rea)?[^a-z0-9>]+([^>]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str);
 			}
 
 			if (preg_match('/<img/i', $str))
@@ -669,6 +676,22 @@ class CI_Security {
 			? ENT_COMPAT | ENT_HTML5
 			: ENT_COMPAT;
 
+		if ( ! isset($_entities))
+		{
+			$_entities = array_map('strtolower', get_html_translation_table(HTML_ENTITIES, $flag, $charset));
+
+			// If we're not on PHP 5.4+, add the possibly dangerous HTML 5
+			// entities to the array manually
+			if ($flag === ENT_COMPAT)
+			{
+				$_entities[':'] = '&colon;';
+				$_entities['('] = '&lpar;';
+				$_entities[')'] = '&rpar;';
+				$_entities["\n"] = '&NewLine;';
+				$_entities["\t"] = '&Tab;';
+			}
+		}
+
 		do
 		{
 			$str_compare = $str;
@@ -676,22 +699,6 @@ class CI_Security {
 			// Decode standard entities, avoiding false positives
 			if (preg_match_all('/&[a-z]{2,}(?![a-z;])/i', $str, $matches))
 			{
-				if ( ! isset($_entities))
-				{
-					$_entities = array_map('strtolower', get_html_translation_table(HTML_ENTITIES, $flag, $charset));
-
-					// If we're not on PHP 5.4+, add the possibly dangerous HTML 5
-					// entities to the array manually
-					if ($flag === ENT_COMPAT)
-					{
-						$_entities[':'] = '&colon;';
-						$_entities['('] = '&lpar;';
-						$_entities[')'] = '&rpar;';
-						$_entities["\n"] = '&newline;';
-						$_entities["\t"] = '&tab;';
-					}
-				}
-
 				$replace = array();
 				$matches = array_unique(array_map('strtolower', $matches[0]));
 				foreach ($matches as &$match)
@@ -702,7 +709,7 @@ class CI_Security {
 					}
 				}
 
-				$str = str_ireplace(array_keys($replace), array_values($replace), $str);
+				$str = str_replace(array_keys($replace), array_values($replace), $str);
 			}
 
 			// Decode numeric & UTF16 two byte entities
@@ -711,6 +718,11 @@ class CI_Security {
 				$flag,
 				$charset
 			);
+
+			if ($flag === ENT_COMPAT)
+			{
+				$str = str_replace(array_values($_entities), array_keys($_entities), $str);
+			}
 		}
 		while ($str_compare !== $str);
 		return $str;
@@ -770,6 +782,24 @@ class CI_Security {
 	// ----------------------------------------------------------------
 
 	/**
+	 * URL-decode taking spaces into account
+	 *
+	 * @see		https://github.com/bcit-ci/CodeIgniter/issues/4877
+	 * @param	array	$matches
+	 * @return	string
+	 */
+	protected function _urldecodespaces($matches)
+	{
+		$input    = $matches[0];
+		$nospaces = preg_replace('#\s+#', '', $input);
+		return ($nospaces === $input)
+			? $input
+			: rawurldecode($nospaces);
+	}
+
+	// ----------------------------------------------------------------
+
+	/**
 	 * Compact Exploded Words
 	 *
 	 * Callback method for xss_clean() to remove whitespace from
@@ -798,7 +828,7 @@ class CI_Security {
 	protected function _sanitize_naughty_html($matches)
 	{
 		static $naughty_tags    = array(
-			'alert', 'prompt', 'confirm', 'applet', 'audio', 'basefont', 'base', 'behavior', 'bgsound',
+			'alert', 'area', 'prompt', 'confirm', 'applet', 'audio', 'basefont', 'base', 'behavior', 'bgsound',
 			'blink', 'body', 'embed', 'expression', 'form', 'frameset', 'frame', 'head', 'html', 'ilayer',
 			'iframe', 'input', 'button', 'select', 'isindex', 'layer', 'link', 'meta', 'keygen', 'object',
 			'plaintext', 'style', 'script', 'textarea', 'title', 'math', 'video', 'svg', 'xml', 'xss'
@@ -895,7 +925,7 @@ class CI_Security {
 		return str_replace(
 			$match[1],
 			preg_replace(
-				'#href=.*?(?:(?:alert|prompt|confirm)(?:\(|&\#40;)|javascript:|livescript:|mocha:|charset=|window\.|document\.|\.cookie|<script|<xss|data\s*:)#si',
+				'#href=.*?(?:(?:alert|prompt|confirm)(?:\(|&\#40;)|javascript:|livescript:|mocha:|charset=|window\.|document\.|\.cookie|<script|<xss|d\s*a\s*t\s*a\s*:)#si',
 				'',
 				$this->_filter_attributes($match[1])
 			),
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index 43e8eeac6..6f39cc963 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -918,7 +918,7 @@ abstract class CI_DB_driver {
 	 */
 	public function compile_binds($sql, $binds)
 	{
-		if (empty($binds) OR empty($this->bind_marker) OR strpos($sql, $this->bind_marker) === FALSE)
+		if (empty($this->bind_marker) OR strpos($sql, $this->bind_marker) === FALSE)
 		{
 			return $sql;
 		}
diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index 826aa1ebf..ed6f4b672 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -184,7 +184,7 @@ abstract class CI_DB_forge {
 		{
 			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
 		}
-		elseif ( ! $this->db->query(sprintf($this->_create_database, $db_name, $this->db->char_set, $this->db->dbcollat)))
+		elseif ( ! $this->db->query(sprintf($this->_create_database, $this->db->escape_identifiers($db_name), $this->db->char_set, $this->db->dbcollat)))
 		{
 			return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
 		}
@@ -211,7 +211,7 @@ abstract class CI_DB_forge {
 		{
 			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
 		}
-		elseif ( ! $this->db->query(sprintf($this->_drop_database, $db_name)))
+		elseif ( ! $this->db->query(sprintf($this->_drop_database, $this->db->escape_identifiers($db_name))))
 		{
 			return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
 		}
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 7a008eeb8..5a86ce50f 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -679,7 +679,7 @@ abstract class CI_DB_query_builder extends CI_DB_driver {
 				// value appears not to have been set, assign the test to IS NULL
 				$k .= ' IS NULL';
 			}
-			elseif (preg_match('/\s*(!?=|<>|IS(?:\s+NOT)?)\s*$/i', $k, $match, PREG_OFFSET_CAPTURE))
+			elseif (preg_match('/\s*(!?=|<>|\sIS(?:\s+NOT)?\s)\s*$/i', $k, $match, PREG_OFFSET_CAPTURE))
 			{
 				$k = substr($k, 0, $match[0][1]).($match[1][0] === '=' ? ' IS NULL' : ' IS NOT NULL');
 			}
@@ -1915,7 +1915,7 @@ abstract class CI_DB_query_builder extends CI_DB_driver {
 		$affected_rows = 0;
 		for ($i = 0, $total = count($this->qb_set); $i < $total; $i += $batch_size)
 		{
-			if ($this->query($this->_update_batch($this->protect_identifiers($table, TRUE, NULL, FALSE), array_slice($this->qb_set, $i, $batch_size), $this->protect_identifiers($index))))
+			if ($this->query($this->_update_batch($this->protect_identifiers($table, TRUE, NULL, FALSE), array_slice($this->qb_set, $i, $batch_size), $index)))
 			{
 				$affected_rows += $this->affected_rows();
 			}
@@ -1941,6 +1941,8 @@ abstract class CI_DB_query_builder extends CI_DB_driver {
 	 */
 	protected function _update_batch($table, $values, $index)
 	{
+		$index_escaped = $this->protect_identifiers($index);
+
 		$ids = array();
 		foreach ($values as $key => $val)
 		{
@@ -1950,7 +1952,7 @@ abstract class CI_DB_query_builder extends CI_DB_driver {
 			{
 				if ($field !== $index)
 				{
-					$final[$field][] = 'WHEN '.$index.' = '.$val[$index].' THEN '.$val[$field];
+					$final[$field][] = 'WHEN '.$index_escaped.' = '.$val[$index].' THEN '.$val[$field];
 				}
 			}
 		}
@@ -1963,7 +1965,7 @@ abstract class CI_DB_query_builder extends CI_DB_driver {
 				.'ELSE '.$k.' END, ';
 		}
 
-		$this->where($index.' IN('.implode(',', $ids).')', NULL, FALSE);
+		$this->where($index_escaped.' IN('.implode(',', $ids).')', NULL, FALSE);
 
 		return 'UPDATE '.$table.' SET '.substr($cases, 0, -2).$this->_compile_wh('qb_where');
 	}
diff --git a/system/database/drivers/ibase/ibase_driver.php b/system/database/drivers/ibase/ibase_driver.php
index c1055c1e6..671a353bc 100644
--- a/system/database/drivers/ibase/ibase_driver.php
+++ b/system/database/drivers/ibase/ibase_driver.php
@@ -384,6 +384,23 @@ class CI_DB_ibase_driver extends CI_DB {
 	// --------------------------------------------------------------------
 
 	/**
+	 * Insert batch statement
+	 *
+	 * Generates a platform-specific insert string from the supplied data.
+	 *
+	 * @param	string	$table	Table name
+	 * @param	array	$keys	INSERT keys
+	 * @param	array	$values	INSERT values
+	 * @return	string|bool
+	 */
+	protected function _insert_batch($table, $keys, $values)
+	{
+		return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Close DB Connection
 	 *
 	 * @return	void
diff --git a/system/database/drivers/ibase/ibase_forge.php b/system/database/drivers/ibase/ibase_forge.php
index 9c358c365..b35cc3749 100644
--- a/system/database/drivers/ibase/ibase_forge.php
+++ b/system/database/drivers/ibase/ibase_forge.php
@@ -111,7 +111,7 @@ class CI_DB_ibase_forge extends CI_DB_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function drop_database($db_name = '')
+	public function drop_database($db_name)
 	{
 		if ( ! ibase_drop_db($this->conn_id))
 		{
diff --git a/system/database/drivers/odbc/odbc_driver.php b/system/database/drivers/odbc/odbc_driver.php
index 63df2963d..dbce1cf79 100644
--- a/system/database/drivers/odbc/odbc_driver.php
+++ b/system/database/drivers/odbc/odbc_driver.php
@@ -298,7 +298,7 @@ class CI_DB_odbc_driver extends CI_DB_driver {
 	 */
 	public function is_write_type($sql)
 	{
-		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#i', $sql))
+		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#is', $sql))
 		{
 			return FALSE;
 		}
diff --git a/system/database/drivers/pdo/subdrivers/pdo_firebird_driver.php b/system/database/drivers/pdo/subdrivers/pdo_firebird_driver.php
index 96dcc5ec1..7811d3da4 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_firebird_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_firebird_driver.php
@@ -260,4 +260,20 @@ class CI_DB_pdo_firebird_driver extends CI_DB_pdo_driver {
 		return preg_replace('`SELECT`i', 'SELECT '.$select, $sql);
 	}
 
+	// --------------------------------------------------------------------
+
+	/**
+	 * Insert batch statement
+	 *
+	 * Generates a platform-specific insert string from the supplied data.
+	 *
+	 * @param	string	$table	Table name
+	 * @param	array	$keys	INSERT keys
+	 * @param	array	$values	INSERT values
+	 * @return	string|bool
+	 */
+	protected function _insert_batch($table, $keys, $values)
+	{
+		return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
+	}
 }
diff --git a/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php b/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php
index 256fa1413..50df76905 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php
@@ -97,7 +97,7 @@ class CI_DB_pdo_firebird_forge extends CI_DB_pdo_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function drop_database($db_name = '')
+	public function drop_database($db_name)
 	{
 		if ( ! ibase_drop_db($this->conn_id))
 		{
diff --git a/system/database/drivers/pdo/subdrivers/pdo_mysql_driver.php b/system/database/drivers/pdo/subdrivers/pdo_mysql_driver.php
index 3631cdf7a..6452b787b 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_mysql_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_mysql_driver.php
@@ -216,6 +216,55 @@ class CI_DB_pdo_mysql_driver extends CI_DB_pdo_driver {
 	// --------------------------------------------------------------------
 
 	/**
+	 * Begin Transaction
+	 *
+	 * @return	bool
+	 */
+	protected function _trans_begin()
+	{
+		$this->conn_id->setAttribute(PDO::ATTR_AUTOCOMMIT, FALSE);
+		return $this->conn_id->beginTransaction();
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Commit Transaction
+	 *
+	 * @return	bool
+	 */
+	protected function _trans_commit()
+	{
+		if ($this->conn_id->commit())
+		{
+			$this->conn_id->setAttribute(PDO::ATTR_AUTOCOMMIT, TRUE);
+			return TRUE;
+		}
+
+		return FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Rollback Transaction
+	 *
+	 * @return	bool
+	 */
+	protected function _trans_rollback()
+	{
+		if ($this->conn_id->rollBack())
+		{
+			$this->conn_id->setAttribute(PDO::ATTR_AUTOCOMMIT, TRUE);
+			return TRUE;
+		}
+
+		return FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Show table query
 	 *
 	 * Generates a platform-specific query string so that the table names can be fetched
diff --git a/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php b/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php
index 82554ec80..ebe1ed6f0 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_odbc_driver.php
@@ -181,7 +181,7 @@ class CI_DB_pdo_odbc_driver extends CI_DB_pdo_driver {
 	 */
 	public function is_write_type($sql)
 	{
-		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#i', $sql))
+		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#is', $sql))
 		{
 			return FALSE;
 		}
diff --git a/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php b/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php
index ee8f76348..9483d2457 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_pgsql_driver.php
@@ -154,7 +154,7 @@ class CI_DB_pdo_pgsql_driver extends CI_DB_pdo_driver {
 	 */
 	public function is_write_type($sql)
 	{
-		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#i', $sql))
+		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#is', $sql))
 		{
 			return FALSE;
 		}
diff --git a/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php b/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php
index f6f9bb481..b124bcad1 100644
--- a/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php
+++ b/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php
@@ -101,7 +101,7 @@ class CI_DB_pdo_sqlite_forge extends CI_DB_pdo_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function create_database($db_name = '')
+	public function create_database($db_name)
 	{
 		// In SQLite, a database is created when you connect to the database.
 		// We'll return TRUE so that an error isn't generated
@@ -116,7 +116,7 @@ class CI_DB_pdo_sqlite_forge extends CI_DB_pdo_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function drop_database($db_name = '')
+	public function drop_database($db_name)
 	{
 		// In SQLite, a database is dropped when we delete a file
 		if (file_exists($this->db->database))
diff --git a/system/database/drivers/postgre/postgre_driver.php b/system/database/drivers/postgre/postgre_driver.php
index ce21260ef..c7c827ea4 100644
--- a/system/database/drivers/postgre/postgre_driver.php
+++ b/system/database/drivers/postgre/postgre_driver.php
@@ -282,7 +282,7 @@ class CI_DB_postgre_driver extends CI_DB {
 	 */
 	public function is_write_type($sql)
 	{
-		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#i', $sql))
+		if (preg_match('#^(INSERT|UPDATE).*RETURNING\s.+(\,\s?.+)*$#is', $sql))
 		{
 			return FALSE;
 		}
diff --git a/system/database/drivers/sqlite/sqlite_forge.php b/system/database/drivers/sqlite/sqlite_forge.php
index 8a1659430..3ad3477e4 100644
--- a/system/database/drivers/sqlite/sqlite_forge.php
+++ b/system/database/drivers/sqlite/sqlite_forge.php
@@ -75,7 +75,7 @@ class CI_DB_sqlite_forge extends CI_DB_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function create_database($db_name = '')
+	public function create_database($db_name)
 	{
 		// In SQLite, a database is created when you connect to the database.
 		// We'll return TRUE so that an error isn't generated
@@ -90,7 +90,7 @@ class CI_DB_sqlite_forge extends CI_DB_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function drop_database($db_name = '')
+	public function drop_database($db_name)
 	{
 		if ( ! file_exists($this->db->database) OR ! @unlink($this->db->database))
 		{
diff --git a/system/database/drivers/sqlite3/sqlite3_forge.php b/system/database/drivers/sqlite3/sqlite3_forge.php
index 43cbe33e5..c45472f54 100644
--- a/system/database/drivers/sqlite3/sqlite3_forge.php
+++ b/system/database/drivers/sqlite3/sqlite3_forge.php
@@ -87,7 +87,7 @@ class CI_DB_sqlite3_forge extends CI_DB_forge {
 	 * @param	string	$db_name
 	 * @return	bool
 	 */
-	public function create_database($db_name = '')
+	public function create_database($db_name)
 	{
 		// In SQLite, a database is created when you connect to the database.
 		// We'll return TRUE so that an error isn't generated
@@ -102,7 +102,7 @@ class CI_DB_sqlite3_forge extends CI_DB_forge {
 	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
-	public function drop_database($db_name = '')
+	public function drop_database($db_name)
 	{
 		// In SQLite, a database is dropped when we delete a file
 		if (file_exists($this->db->database))
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 6a7e2b3a7..525a1277e 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -374,6 +374,13 @@ class CI_Email {
 		5 => '5 (Lowest)'
 	);
 
+	/**
+	 * mbstring.func_override flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_override;
+
 	// --------------------------------------------------------------------
 
 	/**
@@ -390,6 +397,8 @@ class CI_Email {
 		$this->initialize($config);
 		$this->_safe_mode = ( ! is_php('5.4') && ini_get('safe_mode'));
 
+		isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));
+
 		log_message('info', 'Email Class Initialized');
 	}
 
@@ -1037,7 +1046,7 @@ class CI_Email {
 	{
 		if (function_exists('idn_to_ascii') && $atpos = strpos($email, '@'))
 		{
-			$email = substr($email, 0, ++$atpos).idn_to_ascii(substr($email, $atpos));
+			$email = self::substr($email, 0, ++$atpos).idn_to_ascii(self::substr($email, $atpos));
 		}
 
 		return (bool) filter_var($email, FILTER_VALIDATE_EMAIL);
@@ -1154,7 +1163,7 @@ class CI_Email {
 		{
 			// Is the line within the allowed character count?
 			// If so we'll join it to the output and continue
-			if (mb_strlen($line) <= $charlim)
+			if (self::strlen($line) <= $charlim)
 			{
 				$output .= $line.$this->newline;
 				continue;
@@ -1170,10 +1179,10 @@ class CI_Email {
 				}
 
 				// Trim the word down
-				$temp .= mb_substr($line, 0, $charlim - 1);
-				$line = mb_substr($line, $charlim - 1);
+				$temp .= self::substr($line, 0, $charlim - 1);
+				$line = self::substr($line, $charlim - 1);
 			}
-			while (mb_strlen($line) > $charlim);
+			while (self::strlen($line) > $charlim);
 
 			// If $temp contains data it means we had to split up an over-length
 			// word into smaller chunks so we'll add it back to our current line
@@ -1385,7 +1394,7 @@ class CI_Email {
 					$this->_header_str .= $hdr;
 				}
 
-				strlen($body) && $body .= $this->newline.$this->newline;
+				self::strlen($body) && $body .= $this->newline.$this->newline;
 				$body .= $this->_get_mime_message().$this->newline.$this->newline
 					.'--'.$last_boundary.$this->newline
 
@@ -1532,7 +1541,7 @@ class CI_Email {
 
 		foreach (explode("\n", $str) as $line)
 		{
-			$length = strlen($line);
+			$length = self::strlen($line);
 			$temp = '';
 
 			// Loop through each character in the line to add soft-wrap
@@ -1567,7 +1576,7 @@ class CI_Email {
 
 				// If we're at the character limit, add the line to the output,
 				// reset our temp variable, and keep on chuggin'
-				if ((strlen($temp) + strlen($char)) >= 76)
+				if ((self::strlen($temp) + self::strlen($char)) >= 76)
 				{
 					$output .= $temp.$escape.$this->crlf;
 					$temp = '';
@@ -1582,7 +1591,7 @@ class CI_Email {
 		}
 
 		// get rid of extra CRLF tacked onto the end
-		return substr($output, 0, strlen($this->crlf) * -1);
+		return self::substr($output, 0, self::strlen($this->crlf) * -1);
 	}
 
 	// --------------------------------------------------------------------
@@ -1624,7 +1633,7 @@ class CI_Email {
 					// iconv_mime_encode() will always put a header field name.
 					// We've passed it an empty one, but it still prepends our
 					// encoded string with ': ', so we need to strip it.
-					return substr($output, 2);
+					return self::substr($output, 2);
 				}
 
 				$chars = iconv_strlen($str, 'UTF-8');
@@ -1636,10 +1645,10 @@ class CI_Email {
 		}
 
 		// We might already have this set for UTF-8
-		isset($chars) OR $chars = strlen($str);
+		isset($chars) OR $chars = self::strlen($str);
 
 		$output = '=?'.$this->charset.'?Q?';
-		for ($i = 0, $length = strlen($output); $i < $chars; $i++)
+		for ($i = 0, $length = self::strlen($output); $i < $chars; $i++)
 		{
 			$chr = ($this->charset === 'UTF-8' && ICONV_ENABLED === TRUE)
 				? '='.implode('=', str_split(strtoupper(bin2hex(iconv_substr($str, $i, 1, $this->charset))), 2))
@@ -1647,11 +1656,11 @@ class CI_Email {
 
 			// RFC 2045 sets a limit of 76 characters per line.
 			// We'll append ?= to the end of each line though.
-			if ($length + ($l = strlen($chr)) > 74)
+			if ($length + ($l = self::strlen($chr)) > 74)
 			{
 				$output .= '?='.$this->crlf // EOL
 					.' =?'.$this->charset.'?Q?'.$chr; // New line
-				$length = 6 + strlen($this->charset) + $l; // Reset the length for the new line
+				$length = 6 + self::strlen($this->charset) + $l; // Reset the length for the new line
 			}
 			else
 			{
@@ -1744,14 +1753,14 @@ class CI_Email {
 
 			if ($i === $float)
 			{
-				$chunk[] = substr($set, 1);
+				$chunk[] = self::substr($set, 1);
 				$float += $this->bcc_batch_size;
 				$set = '';
 			}
 
 			if ($i === $c-1)
 			{
-				$chunk[] = substr($set, 1);
+				$chunk[] = self::substr($set, 1);
 			}
 		}
 
@@ -2109,7 +2118,7 @@ class CI_Email {
 
 		$this->_debug_msg[] = '<pre>'.$cmd.': '.$reply.'</pre>';
 
-		if ((int) substr($reply, 0, 3) !== $resp)
+		if ((int) self::substr($reply, 0, 3) !== $resp)
 		{
 			$this->_set_error_message('lang:email_smtp_error', $reply);
 			return FALSE;
@@ -2196,9 +2205,9 @@ class CI_Email {
 	protected function _send_data($data)
 	{
 		$data .= $this->newline;
-		for ($written = $timestamp = 0, $length = strlen($data); $written < $length; $written += $result)
+		for ($written = $timestamp = 0, $length = self::strlen($data); $written < $length; $written += $result)
 		{
-			if (($result = fwrite($this->_smtp_connect, substr($data, $written))) === FALSE)
+			if (($result = fwrite($this->_smtp_connect, self::substr($data, $written))) === FALSE)
 			{
 				break;
 			}
@@ -2382,4 +2391,44 @@ class CI_Email {
 	{
 		is_resource($this->_smtp_connect) && $this->_send_command('quit');
 	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_override)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe substr()
+	 *
+	 * @param	string	$str
+	 * @param	int	$start
+	 * @param	int	$length
+	 * @return	string
+	 */
+	protected static function substr($str, $start, $length = NULL)
+	{
+		if (self::$func_override)
+		{
+			// mb_substr($str, $start, null, '8bit') returns an empty
+			// string on PHP 5.3
+			isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
+			return mb_substr($str, $start, $length, '8bit');
+		}
+
+		return isset($length)
+			? substr($str, $start, $length)
+			: substr($str, $start);
+	}
 }
diff --git a/system/libraries/Encryption.php b/system/libraries/Encryption.php
index 06284c2ed..545081b3b 100644
--- a/system/libraries/Encryption.php
+++ b/system/libraries/Encryption.php
@@ -907,7 +907,7 @@ class CI_Encryption {
 	 * Byte-safe strlen()
 	 *
 	 * @param	string	$str
-	 * @return	integer
+	 * @return	int
 	 */
 	protected static function strlen($str)
 	{
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 4380dd276..384caf000 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -1233,9 +1233,9 @@ class CI_Form_validation {
 	 */
 	public function valid_email($str)
 	{
-		if (function_exists('idn_to_ascii') && $atpos = strpos($str, '@'))
+		if (function_exists('idn_to_ascii') && sscanf($str, '%[^@]@%s', $name, $domain) === 2)
 		{
-			$str = substr($str, 0, ++$atpos).idn_to_ascii(substr($str, $atpos));
+			$str = $name.'@'.idn_to_ascii($domain);
 		}
 
 		return (bool) filter_var($str, FILTER_VALIDATE_EMAIL);
diff --git a/system/libraries/Session/Session.php b/system/libraries/Session/Session.php
index 3b391a8ef..01989d2d7 100644
--- a/system/libraries/Session/Session.php
+++ b/system/libraries/Session/Session.php
@@ -57,6 +57,7 @@ class CI_Session {
 
 	protected $_driver = 'files';
 	protected $_config;
+	protected $_sid_regexp;
 
 	// ------------------------------------------------------------------------
 
@@ -99,6 +100,7 @@ class CI_Session {
 
 		// Configuration ...
 		$this->_configure($params);
+		$this->_config['_sid_regexp'] = $this->_sid_regexp;
 
 		$class = new $class($this->_config);
 		if ($class instanceof SessionHandlerInterface)
@@ -131,7 +133,7 @@ class CI_Session {
 		if (isset($_COOKIE[$this->_config['cookie_name']])
 			&& (
 				! is_string($_COOKIE[$this->_config['cookie_name']])
-				OR ! preg_match('/^[0-9a-f]{40}$/', $_COOKIE[$this->_config['cookie_name']])
+				OR ! preg_match('#\A'.$this->_sid_regexp.'\z#', $_COOKIE[$this->_config['cookie_name']])
 			)
 		)
 		{
@@ -315,8 +317,82 @@ class CI_Session {
 		ini_set('session.use_strict_mode', 1);
 		ini_set('session.use_cookies', 1);
 		ini_set('session.use_only_cookies', 1);
-		ini_set('session.hash_function', 1);
-		ini_set('session.hash_bits_per_character', 4);
+
+		$this->_configure_sid_length();
+	}
+
+	// ------------------------------------------------------------------------
+
+	/**
+	 * Configure session ID length
+	 *
+	 * To make life easier, we used to force SHA-1 and 4 bits per
+	 * character on everyone. And of course, someone was unhappy.
+	 *
+	 * Then PHP 7.1 broke backwards-compatibility because ext/session
+	 * is such a mess that nobody wants to touch it with a pole stick,
+	 * and the one guy who does, nobody has the energy to argue with.
+	 *
+	 * So we were forced to make changes, and OF COURSE something was
+	 * going to break and now we have this pile of shit. -- Narf
+	 *
+	 * @return	void
+	 */
+	protected function _configure_sid_length()
+	{
+		if (PHP_VERSION_ID < 70100)
+		{
+			$hash_function = ini_get('session.hash_function');
+			if (ctype_digit($hash_function))
+			{
+				if ($hash_function !== '1')
+				{
+					ini_set('session.hash_function', 1);
+				}
+
+				$bits = 160;
+			}
+			elseif ( ! in_array($hash_function, hash_algos(), TRUE))
+			{
+				ini_set('session.hash_function', 1);
+				$bits = 160;
+			}
+			elseif (($bits = strlen(hash($hash_function, 'dummy', false)) * 4) < 160)
+			{
+				ini_set('session.hash_function', 1);
+				$bits = 160;
+			}
+
+			$bits_per_character = (int) ini_get('session.hash_bits_per_character');
+			$sid_length         = (int) ceil($bits / $bits_per_character);
+		}
+		else
+		{
+			$bits_per_character = (int) ini_get('session.sid_bits_per_character');
+			$sid_length         = (int) ini_get('session.sid_length');
+			if (($bits = $sid_length * $bits_per_character) < 160)
+			{
+				// Add as many more characters as necessary to reach at least 160 bits
+				$sid_length += (int) ceil((160 % $bits) / $bits_per_character);
+				ini_set('session.sid_length', $sid_length);
+			}
+		}
+
+		// Yes, 4,5,6 are the only known possible values as of 2016-10-27
+		switch ($bits_per_character)
+		{
+			case 4:
+				$this->_sid_regexp = '[0-9a-f]';
+				break;
+			case 5:
+				$this->_sid_regexp = '[0-9a-v]';
+				break;
+			case 6:
+				$this->_sid_regexp = '[0-9a-zA-Z,-]';
+				break;
+		}
+
+		$this->_sid_regexp .= '{'.$sid_length.'}';
 	}
 
 	// ------------------------------------------------------------------------
diff --git a/system/libraries/Session/drivers/Session_files_driver.php b/system/libraries/Session/drivers/Session_files_driver.php
index bf4df8b20..37315d3cd 100644
--- a/system/libraries/Session/drivers/Session_files_driver.php
+++ b/system/libraries/Session/drivers/Session_files_driver.php
@@ -76,6 +76,20 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 */
 	protected $_file_new;
 
+	/**
+	 * Validate SID regular expression
+	 *
+	 * @var	string
+	 */
+	protected $_sid_regexp;
+
+	/**
+	 * mbstring.func_override flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_override;
+
 	// ------------------------------------------------------------------------
 
 	/**
@@ -98,6 +112,10 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 			log_message('debug', 'Session: "sess_save_path" is empty; using "session.save_path" value from php.ini.');
 			$this->_config['save_path'] = rtrim(ini_get('session.save_path'), '/\\');
 		}
+
+		$this->_sid_regexp = $this->_config['_sid_regexp'];
+
+		isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));
 	}
 
 	// ------------------------------------------------------------------------
@@ -187,7 +205,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 		}
 
 		$session_data = '';
-		for ($read = 0, $length = filesize($this->_file_path.$session_id); $read < $length; $read += strlen($buffer))
+		for ($read = 0, $length = filesize($this->_file_path.$session_id); $read < $length; $read += self::strlen($buffer))
 		{
 			if (($buffer = fread($this->_file_handle, $length - $read)) === FALSE)
 			{
@@ -343,10 +361,13 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 
 		$ts = time() - $maxlifetime;
 
+		$pattern = ($this->_config['match_ip'] === TRUE)
+			? '[0-9a-f]{32}'
+			: '';
+
 		$pattern = sprintf(
-			'/^%s[0-9a-f]{%d}$/',
-			preg_quote($this->_config['cookie_name'], '/'),
-			($this->_config['match_ip'] === TRUE ? 72 : 40)
+			'#\A%s'.$pattern.$this->_sid_regexp.'\z#',
+			preg_quote($this->_config['cookie_name'])
 		);
 
 		while (($file = readdir($directory)) !== FALSE)
@@ -368,4 +389,18 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 		return $this->_success;
 	}
 
-}
\ No newline at end of file
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_override)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+}
diff --git a/system/libraries/Zip.php b/system/libraries/Zip.php
index 140ad7212..25315c92e 100644
--- a/system/libraries/Zip.php
+++ b/system/libraries/Zip.php
@@ -106,12 +106,21 @@ class CI_Zip {
 	public $compression_level = 2;
 
 	/**
+	 * mbstring.func_override flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_override;
+
+	/**
 	 * Initialize zip compression class
 	 *
 	 * @return	void
 	 */
 	public function __construct()
 	{
+		isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));
+
 		$this->now = time();
 		log_message('info', 'Zip Compression Class Initialized');
 	}
@@ -182,7 +191,7 @@ class CI_Zip {
 			.pack('V', 0) // crc32
 			.pack('V', 0) // compressed filesize
 			.pack('V', 0) // uncompressed filesize
-			.pack('v', strlen($dir)) // length of pathname
+			.pack('v', self::strlen($dir)) // length of pathname
 			.pack('v', 0) // extra field length
 			.$dir
 			// below is "data descriptor" segment
@@ -197,7 +206,7 @@ class CI_Zip {
 			.pack('V',0) // crc32
 			.pack('V',0) // compressed filesize
 			.pack('V',0) // uncompressed filesize
-			.pack('v', strlen($dir)) // length of pathname
+			.pack('v', self::strlen($dir)) // length of pathname
 			.pack('v', 0) // extra field length
 			.pack('v', 0) // file comment length
 			.pack('v', 0) // disk number start
@@ -206,7 +215,7 @@ class CI_Zip {
 			.pack('V', $this->offset) // relative offset of local header
 			.$dir;
 
-		$this->offset = strlen($this->zipdata);
+		$this->offset = self::strlen($this->zipdata);
 		$this->entries++;
 	}
 
@@ -255,10 +264,10 @@ class CI_Zip {
 	{
 		$filepath = str_replace('\\', '/', $filepath);
 
-		$uncompressed_size = strlen($data);
+		$uncompressed_size = self::strlen($data);
 		$crc32  = crc32($data);
-		$gzdata = substr(gzcompress($data, $this->compression_level), 2, -4);
-		$compressed_size = strlen($gzdata);
+		$gzdata = self::substr(gzcompress($data, $this->compression_level), 2, -4);
+		$compressed_size = self::strlen($gzdata);
 
 		$this->zipdata .=
 			"\x50\x4b\x03\x04\x14\x00\x00\x00\x08\x00"
@@ -267,7 +276,7 @@ class CI_Zip {
 			.pack('V', $crc32)
 			.pack('V', $compressed_size)
 			.pack('V', $uncompressed_size)
-			.pack('v', strlen($filepath)) // length of filename
+			.pack('v', self::strlen($filepath)) // length of filename
 			.pack('v', 0) // extra field length
 			.$filepath
 			.$gzdata; // "file data" segment
@@ -279,7 +288,7 @@ class CI_Zip {
 			.pack('V', $crc32)
 			.pack('V', $compressed_size)
 			.pack('V', $uncompressed_size)
-			.pack('v', strlen($filepath)) // length of filename
+			.pack('v', self::strlen($filepath)) // length of filename
 			.pack('v', 0) // extra field length
 			.pack('v', 0) // file comment length
 			.pack('v', 0) // disk number start
@@ -288,7 +297,7 @@ class CI_Zip {
 			.pack('V', $this->offset) // relative offset of local header
 			.$filepath;
 
-		$this->offset = strlen($this->zipdata);
+		$this->offset = self::strlen($this->zipdata);
 		$this->entries++;
 		$this->file_num++;
 	}
@@ -401,8 +410,8 @@ class CI_Zip {
 			.$this->directory."\x50\x4b\x05\x06\x00\x00\x00\x00"
 			.pack('v', $this->entries) // total # of entries "on this disk"
 			.pack('v', $this->entries) // total # of entries overall
-			.pack('V', strlen($this->directory)) // size of central dir
-			.pack('V', strlen($this->zipdata)) // offset to start of central dir
+			.pack('V', self::strlen($this->directory)) // size of central dir
+			.pack('V', self::strlen($this->zipdata)) // offset to start of central dir
 			."\x00\x00"; // .zip file comment length
 	}
 
@@ -425,9 +434,9 @@ class CI_Zip {
 
 		flock($fp, LOCK_EX);
 
-		for ($result = $written = 0, $data = $this->get_zip(), $length = strlen($data); $written < $length; $written += $result)
+		for ($result = $written = 0, $data = $this->get_zip(), $length = self::strlen($data); $written < $length; $written += $result)
 		{
-			if (($result = fwrite($fp, substr($data, $written))) === FALSE)
+			if (($result = fwrite($fp, self::substr($data, $written))) === FALSE)
 			{
 				break;
 			}
@@ -481,4 +490,43 @@ class CI_Zip {
 		return $this;
 	}
 
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_override)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe substr()
+	 *
+	 * @param	string	$str
+	 * @param	int	$start
+	 * @param	int	$length
+	 * @return	string
+	 */
+	protected static function substr($str, $start, $length = NULL)
+	{
+		if (self::$func_override)
+		{
+			// mb_substr($str, $start, null, '8bit') returns an empty
+			// string on PHP 5.3
+			isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
+			return mb_substr($str, $start, $length, '8bit');
+		}
+
+		return isset($length)
+			? substr($str, $start, $length)
+			: substr($str, $start);
+	}
 }