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<div class="section" id="error-handling">
<h1>Error Handling<a class="headerlink" href="#error-handling" title="Permalink to this headline">¶</a></h1>
<p>CodeIgniter lets you build error reporting into your applications using
the functions described below. In addition, it has an error logging
class that permits error and debugging messages to be saved as text
files.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">By default, CodeIgniter displays all PHP errors. You might
wish to change this behavior once your development is complete. You’ll
find the error_reporting() function located at the top of your main
index.php file. Disabling error reporting will NOT prevent log files
from being written if there are errors.</p>
</div>
<p>Unlike most systems in CodeIgniter, the error functions are simple
procedural interfaces that are available globally throughout the
application. This approach permits error messages to get triggered
without having to worry about class/function scoping.</p>
<p>CodeIgniter also returns a status code whenever a portion of the core
calls <code class="docutils literal"><span class="pre">exit()</span></code>. This exit status code is separate from the HTTP status
code, and serves as a notice to other processes that may be watching of
whether the script completed successfully, or if not, what kind of
problem it encountered that caused it to abort. These values are
defined in <em>application/config/constants.php</em>. While exit status codes
are most useful in CLI settings, returning the proper code helps server
software keep track of your scripts and the health of your application.</p>
<p>The following functions let you generate errors:</p>
<dl class="function">
<dt id="show_error">
<code class="descname">show_error</code><span class="sig-paren">(</span><em>$message</em>, <em>$status_code</em>, <em>$heading = 'An Error Was Encountered'</em><span class="sig-paren">)</span><a class="headerlink" href="#show_error" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$message</strong> (<em>mixed</em>) – Error message</li>
<li><strong>$status_code</strong> (<em>int</em>) – HTTP Response status code</li>
<li><strong>$heading</strong> (<em>string</em>) – Error page heading</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">void</p>
</td>
</tr>
</tbody>
</table>
<p>This function will display the error message supplied to it using
the error template appropriate to your execution:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nx">application</span><span class="o">/</span><span class="nx">views</span><span class="o">/</span><span class="nx">errors</span><span class="o">/</span><span class="nx">html</span><span class="o">/</span><span class="nx">error_general</span><span class="o">.</span><span class="nx">php</span>
</pre></div>
</div>
<p>or:</p>
<blockquote>
<div>application/views/errors/cli/error_general.php</div></blockquote>
<p>The optional parameter <code class="docutils literal"><span class="pre">$status_code</span></code> determines what HTTP status
code should be sent with the error. If <code class="docutils literal"><span class="pre">$status_code</span></code> is less
than 100, the HTTP status code will be set to 500, and the exit
status code will be set to <code class="docutils literal"><span class="pre">$status_code</span> <span class="pre">+</span> <span class="pre">EXIT__AUTO_MIN</span></code>.
If that value is larger than <code class="docutils literal"><span class="pre">EXIT__AUTO_MAX</span></code>, or if
<code class="docutils literal"><span class="pre">$status_code</span></code> is 100 or higher, the exit status code will be set
to <code class="docutils literal"><span class="pre">EXIT_ERROR</span></code>.
You can check in <em>application/config/constants.php</em> for more detail.</p>
</dd></dl>
<dl class="function">
<dt id="show_404">
<code class="descname">show_404</code><span class="sig-paren">(</span><em>$page = ''</em>, <em>$log_error = TRUE</em><span class="sig-paren">)</span><a class="headerlink" href="#show_404" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$page</strong> (<em>string</em>) – URI string</li>
<li><strong>$log_error</strong> (<em>bool</em>) – Whether to log the error</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">void</p>
</td>
</tr>
</tbody>
</table>
<p>This function will display the 404 error message supplied to it
using the error template appropriate to your execution:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nx">application</span><span class="o">/</span><span class="nx">views</span><span class="o">/</span><span class="nx">errors</span><span class="o">/</span><span class="nx">html</span><span class="o">/</span><span class="nx">error_404</span><span class="o">.</span><span class="nx">php</span>
</pre></div>
</div>
<p>or:</p>
<blockquote>
<div>application/views/errors/cli/error_404.php</div></blockquote>
<p>The function expects the string passed to it to be the file path to
the page that isn’t found. The exit status code will be set to
<code class="docutils literal"><span class="pre">EXIT_UNKNOWN_FILE</span></code>.
Note that CodeIgniter automatically shows 404 messages if
controllers are not found.</p>
<p>CodeIgniter automatically logs any <code class="docutils literal"><span class="pre">show_404()</span></code> calls. Setting the
optional second parameter to FALSE will skip logging.</p>
</dd></dl>
<dl class="function">
<dt id="log_message">
<code class="descname">log_message</code><span class="sig-paren">(</span><em>$level</em>, <em>$message</em><span class="sig-paren">)</span><a class="headerlink" href="#log_message" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$level</strong> (<em>string</em>) – Log level: ‘error’, ‘debug’ or ‘info’</li>
<li><strong>$message</strong> (<em>string</em>) – Message to log</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">void</p>
</td>
</tr>
</tbody>
</table>
<p>This function lets you write messages to your log files. You must
supply one of three “levels” in the first parameter, indicating what
type of message it is (debug, error, info), with the message itself
in the second parameter.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="p">(</span><span class="nv">$some_var</span> <span class="o">==</span> <span class="s1">''</span><span class="p">)</span>
<span class="p">{</span>
<span class="nx">log_message</span><span class="p">(</span><span class="s1">'error'</span><span class="p">,</span> <span class="s1">'Some variable did not contain a value.'</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">else</span>
<span class="p">{</span>
<span class="nx">log_message</span><span class="p">(</span><span class="s1">'debug'</span><span class="p">,</span> <span class="s1">'Some variable was correctly set'</span><span class="p">);</span>
<span class="p">}</span>
<span class="nx">log_message</span><span class="p">(</span><span class="s1">'info'</span><span class="p">,</span> <span class="s1">'The purpose of some variable is to provide some value.'</span><span class="p">);</span>
</pre></div>
</div>
<p>There are three message types:</p>
<ol class="arabic simple">
<li>Error Messages. These are actual errors, such as PHP errors or
user errors.</li>
<li>Debug Messages. These are messages that assist in debugging. For
example, if a class has been initialized, you could log this as
debugging info.</li>
<li>Informational Messages. These are the lowest priority messages,
simply giving information regarding some process.</li>
</ol>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">In order for the log file to actually be written, the
<em>logs/</em> directory must be writable. In addition, you must
set the “threshold” for logging in
<em>application/config/config.php</em>. You might, for example,
only want error messages to be logged, and not the other
two types. If you set it to zero logging will be disabled.</p>
</div>
</dd></dl>
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