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Key Components of CodeIgniter

Last modified on: September 7, 2025

<h1 data-start="508" data-end="553">📝 Key Components of CodeIgniter</h1>
<h2 data-start="555" data-end="572">Introduction</h2>
<p data-start="573" data-end="798">CodeIgniter is a <strong data-start="590" data-end="619">lightweight PHP framework</strong> that simplifies the development of web applications. Its power lies in its <strong data-start="695" data-end="716">modular structure</strong> and <strong data-start="721" data-end="750">well-organized components</strong>, which make coding faster and more efficient.</p>
<p data-start="800" data-end="915">In this article, we&rsquo;ll look at the <strong data-start="835" data-end="868">key components of CodeIgniter</strong> that form the backbone of every application.</p>
<hr data-start="917" data-end="920" />
<h2 data-start="922" data-end="959">🔑 Key Components of CodeIgniter</h2>
<h3 data-start="961" data-end="983">1. <strong data-start="968" data-end="981">Model (M)</strong></h3>
<ul data-start="984" data-end="1176">
<li data-start="984" data-end="1039">
<p data-start="986" data-end="1039">Handles all <strong data-start="998" data-end="1036">data logic and database operations</strong>.</p>
</li>
<li data-start="1040" data-end="1111">
<p data-start="1042" data-end="1111">Responsible for <strong data-start="1058" data-end="1097">CRUD (Create, Read, Update, Delete)</strong> operations.</p>
</li>
<li data-start="1112" data-end="1176">
<p data-start="1114" data-end="1176">Keeps application data separate from the presentation layer.</p>
</li>
</ul>
<p data-start="1178" data-end="1237"><strong data-start="1178" data-end="1235">Example &ndash; Model (<code data-start="1197" data-end="1232">application/models/User_model.php</code>)</strong></p>
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<div class="sticky top-9">
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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>&lt;?php
class User_model extends CI_Model {
    public function get_users() {
        $query = $this-&gt;db-&gt;get('users');
        return $query-&gt;result();
    }
}</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="1409" data-end="1412" />
<h3 data-start="1414" data-end="1435">2. <strong data-start="1421" data-end="1433">View (V)</strong></h3>
<ul data-start="1436" data-end="1561">
<li data-start="1436" data-end="1488">
<p data-start="1438" data-end="1488">Responsible for the <strong data-start="1458" data-end="1480">presentation layer</strong> (UI).</p>
</li>
<li data-start="1489" data-end="1561">
<p data-start="1491" data-end="1561">Displays data sent by the controller in <strong data-start="1531" data-end="1551">HTML, CSS, or JS</strong> format.</p>
</li>
</ul>
<p data-start="1563" data-end="1619"><strong data-start="1563" data-end="1617">Example &ndash; View (<code data-start="1581" data-end="1614">application/views/user_list.php</code>)</strong></p>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
<div class="sticky top-9">
<div class="absolute end-0 bottom-0 flex h-9 items-center pe-2">
<div class="bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs">
<pre class="language-php"><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;&lt;title&gt;User List&lt;/title&gt;&lt;/head&gt;
&lt;body&gt;
    &lt;h2&gt;Registered Users&lt;/h2&gt;
    &lt;ul&gt;
        &lt;?php foreach($users as $user): ?&gt;
            &lt;li&gt;&lt;?php echo $user-&gt;name; ?&gt;&lt;/li&gt;
        &lt;?php endforeach; ?&gt;
    &lt;/ul&gt;
&lt;/body&gt;
&lt;/html&gt;</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="1885" data-end="1888" />
<h3 data-start="1890" data-end="1917">3. <strong data-start="1897" data-end="1915">Controller (C)</strong></h3>
<ul data-start="1918" data-end="2098">
<li data-start="1918" data-end="1958">
<p data-start="1920" data-end="1958">The <strong data-start="1924" data-end="1940">central part</strong> of CodeIgniter.</p>
</li>
<li data-start="1959" data-end="2048">
<p data-start="1961" data-end="2048">Accepts user input, communicates with the <strong data-start="2003" data-end="2012">Model</strong>, and passes data to the <strong data-start="2037" data-end="2045">View</strong>.</p>
</li>
<li data-start="2049" data-end="2098">
<p data-start="2051" data-end="2098">Controls the overall flow of the application.</p>
</li>
</ul>
<p data-start="2100" data-end="2163"><strong data-start="2100" data-end="2161">Example &ndash; Controller (<code data-start="2124" data-end="2158">application/controllers/User.php</code>)</strong></p>
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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>&lt;?php
class User extends CI_Controller {
    public function index() {
        $this-&gt;load-&gt;model('User_model');
        $data['users'] = $this-&gt;User_model-&gt;get_users();
        $this-&gt;load-&gt;view('user_list', $data);
    }
}</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2401" data-end="2404" />
<h3 data-start="2406" data-end="2428">4. <strong data-start="2413" data-end="2426">Libraries</strong></h3>
<ul data-start="2429" data-end="2632">
<li data-start="2429" data-end="2579">
<p data-start="2431" data-end="2496">CodeIgniter comes with <strong data-start="2454" data-end="2476">built-in libraries</strong> for common tasks:</p>
<ul data-start="2499" data-end="2579">
<li data-start="2499" data-end="2508">
<p data-start="2501" data-end="2508">Email</p>
</li>
<li data-start="2511" data-end="2522">
<p data-start="2513" data-end="2522">Session</p>
</li>
<li data-start="2525" data-end="2540">
<p data-start="2527" data-end="2540">File Upload</p>
</li>
<li data-start="2543" data-end="2557">
<p data-start="2545" data-end="2557">Pagination</p>
</li>
<li data-start="2560" data-end="2579">
<p data-start="2562" data-end="2579">Form Validation</p>
</li>
</ul>
</li>
<li data-start="2580" data-end="2632">
<p data-start="2582" data-end="2632">Developers can also create <strong data-start="2609" data-end="2629">custom libraries</strong>.</p>
</li>
</ul>
<hr data-start="2634" data-end="2637" />
<h3 data-start="2639" data-end="2659">5. <strong data-start="2646" data-end="2657">Helpers</strong></h3>
<ul data-start="2660" data-end="2897">
<li data-start="2660" data-end="2867">
<p data-start="2662" data-end="2731">A collection of <strong data-start="2678" data-end="2702">procedural functions</strong> that help with tasks like:</p>
<ul data-start="2734" data-end="2867">
<li data-start="2734" data-end="2783">
<p data-start="2736" data-end="2783">Form creation (<code data-start="2751" data-end="2764">form_open()</code>, <code data-start="2766" data-end="2780">form_close()</code>)</p>
</li>
<li data-start="2786" data-end="2833">
<p data-start="2788" data-end="2833">URL management (<code data-start="2804" data-end="2816">base_url()</code>, <code data-start="2818" data-end="2830">site_url()</code>)</p>
</li>
<li data-start="2836" data-end="2867">
<p data-start="2838" data-end="2867">String and array operations</p>
</li>
</ul>
</li>
<li data-start="2868" data-end="2897">
<p data-start="2870" data-end="2897">Easy to load when needed:</p>
</li>
</ul>
<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">&nbsp;</div>
</div>
</div>
<div class="overflow-y-auto p-4" dir="ltr"><code class="whitespace-pre! language-php"><span class="hljs-variable language_">$this</span>-&gt;load-&gt;<span class="hljs-title function_ invoke__">helper</span>(<span class="hljs-string">'url'</span>);
</code></div>
</div>
<hr data-start="2938" data-end="2941" />
<h3 data-start="2943" data-end="2969">6. <strong data-start="2950" data-end="2967">Configuration</strong></h3>
<ul data-start="2970" data-end="3223">
<li data-start="2970" data-end="3011">
<p data-start="2972" data-end="3011">Centralized in <code data-start="2987" data-end="3008">application/config/</code>.</p>
</li>
<li data-start="3012" data-end="3223">
<p data-start="3014" data-end="3046">Important configuration files:</p>
<ul data-start="3049" data-end="3223">
<li data-start="3049" data-end="3105">
<p data-start="3051" data-end="3105"><code data-start="3051" data-end="3063">config.php</code> &rarr; Base URL, index page, encryption key.</p>
</li>
<li data-start="3108" data-end="3158">
<p data-start="3110" data-end="3158"><code data-start="3110" data-end="3124">database.php</code> &rarr; Database connection settings.</p>
</li>
<li data-start="3161" data-end="3223">
<p data-start="3163" data-end="3223"><code data-start="3163" data-end="3177">autoload.php</code> &rarr; Auto-load libraries, helpers, and models.</p>
</li>
</ul>
</li>
</ul>
<hr data-start="3225" data-end="3228" />
<h3 data-start="3230" data-end="3250">7. <strong data-start="3237" data-end="3248">Routing</strong></h3>
<ul data-start="3251" data-end="3359">
<li data-start="3251" data-end="3295">
<p data-start="3253" data-end="3295">Manages how <strong data-start="3265" data-end="3292">URLs map to controllers</strong>.</p>
</li>
<li data-start="3296" data-end="3346">
<p data-start="3298" data-end="3346">Controlled by <code data-start="3312" data-end="3343">application/config/routes.php</code>.</p>
</li>
<li data-start="3347" data-end="3359">
<p data-start="3349" data-end="3359">Example:</p>
</li>
</ul>
<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">&nbsp;</div>
</div>
</div>
<div class="overflow-y-auto p-4" dir="ltr"><code class="whitespace-pre! language-php"><span class="hljs-variable">$route</span>[<span class="hljs-string">'users'</span>] = <span class="hljs-string">'user/index'</span>;
</code></div>
</div>
<p data-start="3403" data-end="3485">👉 This routes <code data-start="3418" data-end="3444">http://example.com/users</code> to <code data-start="3448" data-end="3475">User Controller &rarr; index()</code> method.</p>
<hr data-start="3487" data-end="3490" />
<h3 data-start="3492" data-end="3529">8. <strong data-start="3499" data-end="3527">Error Handling &amp; Logging</strong></h3>
<ul data-start="3530" data-end="3698">
<li data-start="3530" data-end="3595">
<p data-start="3532" data-end="3595">CodeIgniter provides flexible <strong data-start="3562" data-end="3592">error handling and logging</strong>.</p>
</li>
<li data-start="3596" data-end="3677">
<p data-start="3598" data-end="3677">Developers can control error reporting levels in <code data-start="3647" data-end="3658">index.php</code> or <code data-start="3662" data-end="3674">config.php</code>.</p>
</li>
<li data-start="3678" data-end="3698">
<p data-start="3680" data-end="3698">Useful function:</p>
</li>
</ul>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
<div class="sticky top-9">
<div class="absolute end-0 bottom-0 flex h-9 items-center pe-2">
<div class="bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs">
<pre class="language-php"><code>$this-&gt;load-&gt;helper('url');</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="3758" data-end="3761" />
<h3 data-start="3763" data-end="3793">9. <strong data-start="3770" data-end="3791">Security Features</strong></h3>
<ul data-start="3794" data-end="3923">
<li data-start="3794" data-end="3836">
<p data-start="3796" data-end="3836"><strong data-start="3796" data-end="3813">XSS filtering</strong> to clean user input.</p>
</li>
<li data-start="3837" data-end="3871">
<p data-start="3839" data-end="3871"><strong data-start="3839" data-end="3858">CSRF protection</strong> for forms.</p>
</li>
<li data-start="3872" data-end="3923">
<p data-start="3874" data-end="3923">SQL query binding to prevent <strong data-start="3903" data-end="3920">SQL injection</strong>.</p>
</li>
</ul>
<hr data-start="3925" data-end="3928" />
<h2 data-start="3930" data-end="3972">🚀 How These Components Work Together</h2>
<ol data-start="3973" data-end="4249">
<li data-start="3973" data-end="4035">
<p data-start="3976" data-end="4035"><strong data-start="3976" data-end="4000">User requests a page</strong> &rarr; Router decides the controller.</p>
</li>
<li data-start="4036" data-end="4102">
<p data-start="4039" data-end="4102"><strong data-start="4039" data-end="4071">Controller processes request</strong> &rarr; Loads model to fetch data.</p>
</li>
<li data-start="4103" data-end="4174">
<p data-start="4106" data-end="4174"><strong data-start="4106" data-end="4139">Model interacts with database</strong> &rarr; Sends data back to controller.</p>
</li>
<li data-start="4175" data-end="4249">
<p data-start="4178" data-end="4249"><strong data-start="4178" data-end="4212">Controller passes data to View</strong> &rarr; Output is displayed to the user.</p>
</li>
</ol>
<hr data-start="4251" data-end="4254" />
<h2 data-start="4256" data-end="4271">Conclusion</h2>
<p data-start="4272" data-end="4453">The <strong data-start="4276" data-end="4309">key components of CodeIgniter</strong> &mdash; MVC, Libraries, Helpers, Configuration, Routing, and Security &mdash; work together to make web development <strong data-start="4414" data-end="4450">faster, cleaner, and more secure</strong>.</p>
<p data-start="4455" data-end="4552">Understanding these components is essential for building efficient applications in CodeIgniter.</p>
<p data-start="4554" data-end="4675">If you&rsquo;re new to PHP frameworks, CodeIgniter is the <strong data-start="4606" data-end="4632">perfect starting point</strong> to grasp MVC and structured development.</p>

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