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Error logging configuration

Last modified on: September 9, 2025

<h1 data-start="436" data-end="471">🐞 Error Logging in CodeIgniter</h1>
<h2 data-start="473" data-end="509">🔎 Why Configure Error Logging?</h2>
<p data-start="510" data-end="546">Error logging helps developers to:</p>
<ul data-start="547" data-end="717">
<li data-start="547" data-end="578">
<p data-start="549" data-end="578">Debug issues in development</p>
</li>
<li data-start="579" data-end="622">
<p data-start="581" data-end="622">Monitor unexpected errors in production</p>
</li>
<li data-start="623" data-end="670">
<p data-start="625" data-end="670">Store logs for auditing and troubleshooting</p>
</li>
<li data-start="671" data-end="717">
<p data-start="673" data-end="717">Improve application stability and security</p>
</li>
</ul>
<p data-start="719" data-end="805">Both <strong data-start="724" data-end="741">CodeIgniter 3</strong> and <strong data-start="746" data-end="763">CodeIgniter 4</strong> have powerful error logging mechanisms.</p>
<hr data-start="807" data-end="810" />
<h2 data-start="812" data-end="853">📂 1. Error Logging in CodeIgniter 3</h2>
<h3 data-start="855" data-end="885">Step 1: Open Config File</h3>
<p data-start="886" data-end="893">File:</p>
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<pre class="language-php"><code>application/config/config.php
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="933" data-end="964">Step 2: Set Log Threshold</h3>
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<pre class="language-php"><code>$config['log_threshold'] = 1;
</code></pre>
</div>
</div>
</div>
</div>
<h4 data-start="1007" data-end="1037">🔹 Log Threshold Values</h4>
<ul data-start="1038" data-end="1182">
<li data-start="1038" data-end="1064">
<p data-start="1040" data-end="1064"><code data-start="1040" data-end="1043">0</code> &rarr; Disables logging</p>
</li>
<li data-start="1065" data-end="1086">
<p data-start="1067" data-end="1086"><code data-start="1067" data-end="1070">1</code> &rarr; Errors only</p>
</li>
<li data-start="1087" data-end="1111">
<p data-start="1089" data-end="1111"><code data-start="1089" data-end="1092">2</code> &rarr; Debug messages</p>
</li>
<li data-start="1112" data-end="1144">
<p data-start="1114" data-end="1144"><code data-start="1114" data-end="1117">3</code> &rarr; Informational messages</p>
</li>
<li data-start="1145" data-end="1182">
<p data-start="1147" data-end="1182"><code data-start="1147" data-end="1150">4</code> &rarr; All messages (full logging)</p>
</li>
</ul>
<p data-start="1184" data-end="1223">👉 Example for development (verbose):</p>
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<pre class="language-php"><code>$config['log_threshold'] = 4;
</code></pre>
</div>
</div>
</div>
</div>
<p data-start="1266" data-end="1308">👉 Example for production (errors only):</p>
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<pre class="language-php"><code>$config['log_threshold'] = 1;
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="1351" data-end="1378">Step 3: Log File Path</h3>
<p data-start="1379" data-end="1412">By default, logs are stored in:</p>
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<pre class="language-php"><code>application/logs/
</code></pre>
</div>
</div>
</div>
</div>
<p data-start="1440" data-end="1466">👉 Example log filename:</p>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
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<pre class="language-php"><code>log-2025-09-09.php
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="1495" data-end="1528">Step 4: Log Example in Code</h3>
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<pre class="language-php"><code>log_message('error', 'Database connection failed!');
log_message('debug', 'User model initialized.');
log_message('info', 'New user registered successfully.');
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="1701" data-end="1704" />
<h2 data-start="1706" data-end="1747">📂 2. Error Logging in CodeIgniter 4</h2>
<p data-start="1749" data-end="1816">In CI4, logging is more flexible with <strong data-start="1787" data-end="1813">Monolog-style handlers</strong>.</p>
<h3 data-start="1818" data-end="1848">Step 1: Open Config File</h3>
<p data-start="1849" data-end="1856">File:</p>
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<div class="sticky top-9">
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<pre class="language-php"><code>app/Config/Logger.php
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="1888" data-end="1925">Step 2: Configure Log Threshold</h3>
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<pre class="language-php"><code>public $threshold = 4;
</code></pre>
</div>
</div>
</div>
</div>
<p data-start="1961" data-end="1994">👉 Same meaning as CI3 (<code data-start="1985" data-end="1990">0&ndash;4</code>).</p>
<h3 data-start="1996" data-end="2026">Step 3: Log Storage Path</h3>
<p data-start="2027" data-end="2051">Logs are saved inside:</p>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
<div class="sticky top-9">
<div class="absolute end-0 bottom-0 flex h-9 items-center pe-2">
<div class="bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs">
<pre class="language-php"><code>writable/logs/
</code></pre>
</div>
</div>
</div>
</div>
<p data-start="2076" data-end="2098">👉 Example log file:</p>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
<div class="sticky top-9">
<div class="absolute end-0 bottom-0 flex h-9 items-center pe-2">
<div class="bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs">
<pre class="language-php"><code>log-2025-09-09.log
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="2127" data-end="2160">Step 4: Log Example in Code</h3>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
<div class="sticky top-9">
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<pre class="language-php"><code>log_message('error', 'Payment gateway API failed!');
log_message('debug', 'Order model loaded.');
log_message('info', 'Order placed successfully.');
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2322" data-end="2325" />
<h2 data-start="2327" data-end="2353">📊 CI3 vs CI4 Logging</h2>
<div class="_tableContainer_1rjym_1">
<div class="_tableWrapper_1rjym_13 group flex w-fit flex-col-reverse" tabindex="-1">
<table class="w-fit min-w-(--thread-content-width)" data-start="2355" data-end="3238">
<thead data-start="2355" data-end="2465">
<tr data-start="2355" data-end="2465">
<th data-start="2355" data-end="2379" data-col-size="sm">Feature</th>
<th data-start="2379" data-end="2420" data-col-size="sm">CodeIgniter 3</th>
<th data-start="2420" data-end="2465" data-col-size="sm">CodeIgniter 4</th>
</tr>
</thead>
<tbody data-start="2577" data-end="3238">
<tr data-start="2577" data-end="2687">
<td data-start="2577" data-end="2601" data-col-size="sm">Config File</td>
<td data-start="2601" data-end="2642" data-col-size="sm"><code data-start="2603" data-end="2634">application/config/config.php</code></td>
<td data-start="2642" data-end="2687" data-col-size="sm"><code data-start="2644" data-end="2667">app/Config/Logger.php</code></td>
</tr>
<tr data-start="2688" data-end="2798">
<td data-start="2688" data-end="2712" data-col-size="sm">Log Levels</td>
<td data-start="2712" data-end="2753" data-col-size="sm">0&ndash;4 (error, debug, info, all)</td>
<td data-start="2753" data-end="2798" data-col-size="sm">Same (0&ndash;4) + PSR-3 logging support</td>
</tr>
<tr data-start="2799" data-end="2908">
<td data-start="2799" data-end="2823" data-col-size="sm">Log Path</td>
<td data-start="2823" data-end="2863" data-col-size="sm"><code data-start="2825" data-end="2844">application/logs/</code></td>
<td data-start="2863" data-end="2908" data-col-size="sm"><code data-start="2865" data-end="2881">writable/logs/</code></td>
</tr>
<tr data-start="2909" data-end="3018">
<td data-start="2909" data-end="2933" data-col-size="sm">Log File Format</td>
<td data-start="2933" data-end="2973" data-col-size="sm"><code data-start="2935" data-end="2955">log-YYYY-MM-DD.php</code></td>
<td data-start="2973" data-end="3018" data-col-size="sm"><code data-start="2975" data-end="2995">log-YYYY-MM-DD.log</code></td>
</tr>
<tr data-start="3019" data-end="3128">
<td data-start="3019" data-end="3043" data-col-size="sm">Log Writing</td>
<td data-start="3043" data-end="3083" data-col-size="sm"><code data-start="3045" data-end="3074">log_message('error', 'msg')</code></td>
<td data-start="3083" data-end="3128" data-col-size="sm"><code data-start="3085" data-end="3114">log_message('error', 'msg')</code></td>
</tr>
<tr data-start="3129" data-end="3238">
<td data-start="3129" data-end="3153" data-col-size="sm">Extra Features</td>
<td data-start="3153" data-end="3193" data-col-size="sm">Simple logging</td>
<td data-start="3193" data-end="3238" data-col-size="sm">Supports <strong data-start="3204" data-end="3223">custom handlers</strong> (Syslog, DB)</td>
</tr>
</tbody>
</table>
</div>
</div>
<hr data-start="3240" data-end="3243" />
<h2 data-start="3245" data-end="3266">✅ Best Practices</h2>
<ol data-start="3268" data-end="3693">
<li data-start="3268" data-end="3333">
<p data-start="3271" data-end="3333"><strong data-start="3271" data-end="3296">Use log_threshold = 4</strong> in development for full debugging.</p>
</li>
<li data-start="3334" data-end="3398">
<p data-start="3337" data-end="3398"><strong data-start="3337" data-end="3362">Use log_threshold = 1</strong> in production to log only errors.</p>
</li>
<li data-start="3399" data-end="3464">
<p data-start="3402" data-end="3464">Rotate logs regularly &rarr; CI creates daily logs automatically.</p>
</li>
<li data-start="3465" data-end="3540">
<p data-start="3468" data-end="3540">Store logs in a secure folder (<code data-start="3499" data-end="3517">application/logs</code> or <code data-start="3521" data-end="3536">writable/logs</code>).</p>
</li>
<li data-start="3541" data-end="3635">
<p data-start="3544" data-end="3635">For CI4, consider adding <strong data-start="3569" data-end="3588">custom handlers</strong> (e.g., send critical errors to email/Slack).</p>
</li>
<li data-start="3636" data-end="3693">
<p data-start="3639" data-end="3693">Monitor log file size &mdash; clear old logs periodically.</p>
</li>
</ol>
<hr data-start="3695" data-end="3698" />
<h2 data-start="3700" data-end="3751">🎯 Example: Custom Logging (CI4 with Services)</h2>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
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<div class="bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs">
<pre class="language-php"><code>$logger = service('logger');
$logger-&gt;error('Critical database error occurred');
$logger-&gt;info('User profile updated successfully');
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="3897" data-end="3900" />
<p data-start="3902" data-end="4029">✅ With this setup, you&rsquo;ll always know what&rsquo;s happening in your CodeIgniter app &mdash; whether you&rsquo;re in development or production.</p>

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