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Data flow between MVC components

Last modified on: September 9, 2025

<h1 data-start="475" data-end="529">📝 Data Flow Between MVC Components in CodeIgniter</h1>
<h2 data-start="531" data-end="551">🔎 Introduction</h2>
<p data-start="552" data-end="697">CodeIgniter follows the <strong data-start="576" data-end="622">MVC (Model-View-Controller) design pattern</strong>, which separates <strong data-start="640" data-end="694">business logic, presentation, and request handling</strong>.</p>
<ul data-start="699" data-end="883">
<li data-start="699" data-end="754">
<p data-start="701" data-end="754"><strong data-start="701" data-end="715">Model (M):</strong> Handles database and business logic.</p>
</li>
<li data-start="755" data-end="808">
<p data-start="757" data-end="808"><strong data-start="757" data-end="770">View (V):</strong> Manages presentation (HTML output).</p>
</li>
<li data-start="809" data-end="883">
<p data-start="811" data-end="883"><strong data-start="811" data-end="830">Controller (C):</strong> Connects Models and Views, handling user requests.</p>
</li>
</ul>
<hr data-start="885" data-end="888" />
<h2 data-start="890" data-end="923">📂 1. MVC Data Flow in Steps</h2>
<h3 data-start="925" data-end="942">🔄 Workflow</h3>
<ol data-start="944" data-end="1572">
<li data-start="944" data-end="1028">
<p data-start="947" data-end="965"><strong data-start="947" data-end="963">User Request</strong></p>
<ul data-start="969" data-end="1028">
<li data-start="969" data-end="1028">
<p data-start="971" data-end="1028">A user makes a request via the browser (<code data-start="1011" data-end="1024">/users/list</code>).</p>
</li>
</ul>
</li>
<li data-start="1030" data-end="1128">
<p data-start="1033" data-end="1065"><strong data-start="1033" data-end="1063">Controller Handles Request</strong></p>
<ul data-start="1069" data-end="1128">
<li data-start="1069" data-end="1128">
<p data-start="1071" data-end="1128">The Controller maps the request to a function (method).</p>
</li>
</ul>
</li>
<li data-start="1130" data-end="1227">
<p data-start="1133" data-end="1161"><strong data-start="1133" data-end="1159">Controller Calls Model</strong></p>
<ul data-start="1165" data-end="1227">
<li data-start="1165" data-end="1227">
<p data-start="1167" data-end="1227">The Controller fetches or updates data by calling a Model.</p>
</li>
</ul>
</li>
<li data-start="1229" data-end="1319">
<p data-start="1232" data-end="1267"><strong data-start="1232" data-end="1265">Model Interacts with Database</strong></p>
<ul data-start="1271" data-end="1319">
<li data-start="1271" data-end="1319">
<p data-start="1273" data-end="1319">The Model executes queries and returns data.</p>
</li>
</ul>
</li>
<li data-start="1321" data-end="1422">
<p data-start="1324" data-end="1360"><strong data-start="1324" data-end="1358">Controller Passes Data to View</strong></p>
<ul data-start="1364" data-end="1422">
<li data-start="1364" data-end="1422">
<p data-start="1366" data-end="1422">The Controller prepares data and sends it to the View.</p>
</li>
</ul>
</li>
<li data-start="1424" data-end="1501">
<p data-start="1427" data-end="1452"><strong data-start="1427" data-end="1450">View Renders Output</strong></p>
<ul data-start="1456" data-end="1501">
<li data-start="1456" data-end="1501">
<p data-start="1458" data-end="1501">The View displays HTML with dynamic data.</p>
</li>
</ul>
</li>
<li data-start="1503" data-end="1572">
<p data-start="1506" data-end="1528"><strong data-start="1506" data-end="1526">User Sees Output</strong></p>
<ul data-start="1532" data-end="1572">
<li data-start="1532" data-end="1572">
<p data-start="1534" data-end="1572">The browser shows the response page.</p>
</li>
</ul>
</li>
</ol>
<hr data-start="1574" data-end="1577" />
<h2 data-start="1579" data-end="1606">📊 2. MVC Flow Diagram</h2>
<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>   ┌──────────────┐
   │   User (UI)  │
   └──────┬───────┘
          │ Request (URL)
          ▼
   ┌──────────────┐
   │ Controller   │
   └──────┬───────┘
          │ Calls
          ▼
   ┌──────────────┐
   │   Model      │
   └──────┬───────┘
          │ Returns Data
          ▼
   ┌──────────────┐
   │    View      │
   └──────┬───────┘
          │ Response (HTML)
          ▼
   ┌──────────────┐
   │   Browser    │
   └──────────────┘
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2062" data-end="2065" />
<h2 data-start="2067" data-end="2102">📂 3. Example of MVC Data Flow</h2>
<h3 data-start="2104" data-end="2134">Controller (<code data-start="2120" data-end="2131">Users.php</code>)</h3>
<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>use App\Models\UserModel;

class Users extends BaseController
{
    public function list()
    {
        // Load Model
        $userModel = new UserModel();

// Fetch data from Model
        $data['users'] = $userModel-&gt;findAll();

// Pass data to View
        return view('users_list', $data);
    }
}
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="2466" data-end="2495">Model (<code data-start="2477" data-end="2492">UserModel.php</code>)</h3>
<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>namespace App\Models;
use CodeIgniter\Model;

class UserModel extends Model
{
    protected $table = 'users';
    protected $primaryKey = 'id';
    protected $allowedFields = ['name', 'email', 'status'];
}
</code></pre>
</div>
</div>
</div>
</div>
<h3 data-start="2714" data-end="2743">View (<code data-start="2724" data-end="2740">users_list.php</code>)</h3>
<div class="contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary">
<div class="sticky top-9">
<div class="absolute end-0 bottom-0 flex h-9 items-center pe-2">
<div class="bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs">
<pre class="language-php"><code>&lt;h2&gt;User List&lt;/h2&gt;
&lt;ul&gt;
&lt;?php foreach($users as $user): ?&gt;
    &lt;li&gt;&lt;?= $user['name']; ?&gt; - &lt;?= $user['email']; ?&gt;&lt;/li&gt;
&lt;?php endforeach; ?&gt;
&lt;/ul&gt;
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2902" data-end="2905" />
<h2 data-start="2907" data-end="2927">🔑 4. Key Notes</h2>
<ul data-start="2929" data-end="3194">
<li data-start="2929" data-end="2979">
<p data-start="2931" data-end="2979"><strong data-start="2931" data-end="2953">Controller = Brain</strong> &rarr; Decides what happens.</p>
</li>
<li data-start="2980" data-end="3052">
<p data-start="2982" data-end="3052"><strong data-start="2982" data-end="3004">Model = Data Layer</strong> &rarr; Fetches, inserts, updates, deletes records.</p>
</li>
<li data-start="3053" data-end="3118">
<p data-start="3055" data-end="3118"><strong data-start="3055" data-end="3084">View = Presentation Layer</strong> &rarr; Displays data in HTML format.</p>
</li>
<li data-start="3119" data-end="3194">
<p data-start="3121" data-end="3194">Data <strong data-start="3126" data-end="3191">always flows Controller &rarr; Model &rarr; Controller &rarr; View &rarr; Browser</strong>.</p>
</li>
</ul>
<hr data-start="3196" data-end="3199" />
<h2 data-start="3201" data-end="3221">✅ 5. Conclusion</h2>
<ul data-start="3223" data-end="3442">
<li data-start="3223" data-end="3274">
<p data-start="3225" data-end="3274">MVC ensures a <strong data-start="3239" data-end="3271">clean separation of concerns</strong>.</p>
</li>
<li data-start="3275" data-end="3353">
<p data-start="3277" data-end="3353">Controllers manage requests, Models handle data, and Views display output.</p>
</li>
<li data-start="3354" data-end="3442">
<p data-start="3356" data-end="3442">Following this flow makes CodeIgniter apps <strong data-start="3399" data-end="3439">maintainable, testable, and scalable</strong>.</p>
</li>
</ul>
<p data-start="3444" data-end="3522"><strong data-start="3444" data-end="3459">Flow Recap:</strong><br data-start="3459" data-end="3462" />👉 User &rarr; Controller &rarr; Model &rarr; Controller &rarr; View &rarr; Browser</p>

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