CodeIgniter Home
- What is CodeIgniter?
- Features of CodeIgniter
- Advantages over other PHP frameworks
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CodeIgniter Overview
- Key Components of CodeIgniter
- MVC design pattern explained
- Workflow of a CodeIgniter application
- System and Application folders overview
CodeIgniter Installing CodeIgniter
- System Requirements (PHP, MySQL, Extensions)
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- Folder structure explained
- Setting base URL
- Configuring index.php file
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CodeIgniter Application Architecture
- Folder structure in detail
- Application vs System folders
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CodeIgniter MVC Framework
- Understanding MVC flow
- Codeigniter Creating Controllers
- Creating Views
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- Loading Models and Views
- Data flow between MVC components
CodeIgniter Basic Concepts
- URLs in CodeIgniter
- Default controller setup
- Routing basics
- Auto-loading resources
- Naming conventions
CodeIgniter Configuration
- Configuration files overview
- Base URL and Index page settings
- Encryption key setup
- Codeigniter Database configuration
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- Custom configuration files
CodeIgniter Working with Database
- Database configuration
- Loading database library
- Query Builder class
- Running queries (select, insert, update, delete)
- Active Record class
- Transactions
- Joins, Grouping, Ordering, Limit
- Query bindings
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CodeIgniter Libraries
- Built-in libraries overview
- Loading libraries
- Common libraries: Pagination, Upload, Email, Form Validation, Session, Encryption, Calendar
- Creating custom libraries
CodeIgniter Error Handling
- Error reporting levels
- Custom error pages (404, 500)
- Using log_message()
- Displaying errors in development vs production
CodeIgniter File Uploading
- Upload library setup
- File upload configuration (path, allowed types, max size)
- Handling errors in upload
- Multiple file uploads
- Securing uploads
CodeIgniter Sending Email
- Email library configuration
- Sending emails via SMTP
- Sending attachments
- Sending HTML emails
- Debugging email errors
CodeIgniter Form Validation
- Form validation library overview
- Setting validation rules
- Prepping data before validation
- Error messages customization
- Validation callbacks
- Server-side vs Client-side validation
CodeIgniter Session Management
- Session library configuration
- Storing session data
- Retrieving session data
- Flashdata in sessions
- Database-driven sessions
CodeIgniter Flashdata
- What is Flashdata?
- Creating flashdata messages
- Retrieving flashdata
- Flashdata expiration
CodeIgniter Tempdata
- Difference between flashdata & tempdata
- Creating tempdata
- Retrieving tempdata
- Removing tempdata
CodeIgniter Cookie Management
- Setting cookies
- Retrieving cookies
- Deleting cookies
- Cookie security
CodeIgniter Common Functions
- base_url()
- site_url()
- redirect()
- form_open() & form helper functions
- String helper functions
CodeIgniter Page Caching
- Enabling page caching
- Cache expiration
- Deleting cache files
- Best practices in caching
CodeIgniter Page Redirection
- Redirect helper function
- Permanent vs Temporary redirection
- Redirect with flashdata
CodeIgniter Application Profiling
- Enabling profiler
- Profiler sections (benchmarks, queries, post data, etc.)
- Customizing profiler output
CodeIgniter Benchmarking
- Benchmark class usage
- Measuring script execution time
- Measuring memory usage
- Custom benchmarks
CodeIgniter Adding JS and CSS
- Loading assets in views
- Using base_url() for assets
- Best practices for assets organization
- Versioning assets
CodeIgniter Internationalization
- Language files in CodeIgniter
- Loading language files
- Switching languages dynamically
- Multi-language website structure
CodeIgniter Security
- Input filtering and XSS cleaning
- CSRF protection
- SQL Injection prevention
- Password hashing & encryption
- Secure file uploads
- Using HTTPS with CodeIgniter

Workflow of a CodeIgniter application

System and Application folders overview →

Last modified on: September 7, 2025

<h1 data-start="525" data-end="578">📝 Workflow of a CodeIgniter Application</h1>
<h2 data-start="580" data-end="597">Introduction</h2>
<p data-start="598" data-end="814">CodeIgniter is a <strong data-start="615" data-end="644">lightweight PHP framework</strong> built on the <strong data-start="658" data-end="689">MVC (Model-View-Controller)</strong> architecture. To use it effectively, you need to understand how it handles a <strong data-start="767" data-end="783">user request</strong> and delivers a <strong data-start="799" data-end="811">response</strong>.</p>
<p data-start="816" data-end="927">In this guide, we&rsquo;ll walk through the <strong data-start="854" data-end="895">workflow of a CodeIgniter application</strong>, step by step, with examples.</p>
<hr data-start="929" data-end="932" />
<h2 data-start="934" data-end="978">🔄 Step-by-Step Workflow of CodeIgniter</h2>
<h3 data-start="980" data-end="1017">1. <strong data-start="987" data-end="1015">User Request via Browser</strong></h3>
<ul data-start="1018" data-end="1226">
<li data-start="1018" data-end="1112">
<p data-start="1020" data-end="1112">A user enters a URL in the browser (e.g., <code data-start="1062" data-end="1108">http://example.com/index.php/products/view/5</code>).</p>
</li>
<li data-start="1113" data-end="1226">
<p data-start="1115" data-end="1226">The request is received by <strong data-start="1142" data-end="1155">index.php</strong>, which is the <strong data-start="1170" data-end="1190">front controller</strong> of every CodeIgniter application.</p>
</li>
</ul>
<hr data-start="1228" data-end="1231" />
<h3 data-start="1233" data-end="1274">2. <strong data-start="1240" data-end="1272">Front Controller (index.php)</strong></h3>
<ul data-start="1275" data-end="1471">
<li data-start="1275" data-end="1335">
<p data-start="1277" data-end="1335"><code data-start="1277" data-end="1288">index.php</code> initializes the <strong data-start="1305" data-end="1332">CodeIgniter environment</strong>.</p>
</li>
<li data-start="1336" data-end="1412">
<p data-start="1338" data-end="1412">It loads the <strong data-start="1351" data-end="1365">core files</strong>, error handling, and configuration settings.</p>
</li>
<li data-start="1413" data-end="1471">
<p data-start="1415" data-end="1471">Think of it as the <strong data-start="1434" data-end="1448">entry gate</strong> of your application.</p>
</li>
</ul>
<hr data-start="1473" data-end="1476" />
<h3 data-start="1478" data-end="1498">3. <strong data-start="1485" data-end="1496">Routing</strong></h3>
<ul data-start="1499" data-end="1669">
<li data-start="1499" data-end="1595">
<p data-start="1501" data-end="1595">The <strong data-start="1505" data-end="1515">Router</strong> checks the request against defined routes in <code data-start="1561" data-end="1592">application/config/routes.php</code>.</p>
</li>
<li data-start="1596" data-end="1669">
<p data-start="1598" data-end="1669">It decides which <strong data-start="1615" data-end="1640">controller and method</strong> should handle the request.</p>
</li>
</ul>
<p data-start="1671" data-end="1705"><strong data-start="1671" data-end="1703">Example Route (<code data-start="1688" data-end="1700">routes.php</code>)</strong></p>
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<pre class="language-php"><code>$route['products/(:num)'] = 'products/view/$1';</code></pre>
</div>
</div>
</div>
</div>
<p data-start="1765" data-end="1858">👉 This means visiting <code data-start="1788" data-end="1800">products/5</code> will call the <strong data-start="1815" data-end="1848">Products controller &rarr; view(5)</strong> method.</p>
<hr data-start="1860" data-end="1863" />
<h3 data-start="1865" data-end="1898">4. <strong data-start="1872" data-end="1896">Controller Execution</strong></h3>
<ul data-start="1899" data-end="2036">
<li data-start="1899" data-end="1958">
<p data-start="1901" data-end="1958">The <strong data-start="1905" data-end="1919">controller</strong> is the central part of the workflow.</p>
</li>
<li data-start="1959" data-end="2036">
<p data-start="1961" data-end="2036">It accepts user input, calls models for data, and loads views for output.</p>
</li>
</ul>
<p data-start="2038" data-end="2103"><strong data-start="2038" data-end="2101">Example Controller (<code data-start="2060" data-end="2098">application/controllers/Products.php</code>)</strong></p>
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<pre class="language-php"><code>&lt;?php
class Products extends CI_Controller {
    public function view($id) {
        $this-&gt;load-&gt;model('Product_model');
        $data['product'] = $this-&gt;Product_model-&gt;get_product($id);
        $this-&gt;load-&gt;view('product_view', $data);
    }
}</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2363" data-end="2366" />
<h3 data-start="2368" data-end="2398">5. <strong data-start="2375" data-end="2396">Model Interaction</strong></h3>
<ul data-start="2399" data-end="2478">
<li data-start="2399" data-end="2478">
<p data-start="2401" data-end="2478">The controller calls the <strong data-start="2426" data-end="2435">Model</strong> for database queries and business logic.</p>
</li>
</ul>
<p data-start="2480" data-end="2540"><strong data-start="2480" data-end="2538">Example Model (<code data-start="2497" data-end="2535">application/models/Product_model.php</code>)</strong></p>
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<pre class="language-php"><code>&lt;?php
class Product_model extends CI_Model {
    public function get_product($id) {
        $query = $this-&gt;db-&gt;get_where('products', array('id' =&gt; $id));
        return $query-&gt;row();
    }
}</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2746" data-end="2749" />
<h3 data-start="2751" data-end="2778">6. <strong data-start="2758" data-end="2776">View Rendering</strong></h3>
<ul data-start="2779" data-end="2855">
<li data-start="2779" data-end="2855">
<p data-start="2781" data-end="2855">The controller passes data to a <strong data-start="2813" data-end="2821">View</strong>, which displays it to the user.</p>
</li>
</ul>
<p data-start="2857" data-end="2914"><strong data-start="2857" data-end="2912">Example View (<code data-start="2873" data-end="2909">application/views/product_view.php</code>)</strong></p>
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<pre class="language-php"><code>&lt;h2&gt;&lt;?php echo $product-&gt;name; ?&gt;&lt;/h2&gt;
&lt;p&gt;Price: $&lt;?php echo $product-&gt;price; ?&gt;&lt;/p&gt;
&lt;p&gt;&lt;?php echo $product-&gt;description; ?&gt;&lt;/p&gt;</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="3056" data-end="3059" />
<h3 data-start="3061" data-end="3104">7. <strong data-start="3068" data-end="3102">Final Response Sent to Browser</strong></h3>
<ul data-start="3105" data-end="3227">
<li data-start="3105" data-end="3162">
<p data-start="3107" data-end="3162">The rendered HTML output is sent back to the browser.</p>
</li>
<li data-start="3163" data-end="3227">
<p data-start="3165" data-end="3227">The user sees the final result (e.g., product details page).</p>
</li>
</ul>
<hr data-start="3229" data-end="3232" />
<h2 data-start="3234" data-end="3271">📌 Complete Workflow in Sequence</h2>
<ol data-start="3273" data-end="3672">
<li data-start="3273" data-end="3307">
<p data-start="3276" data-end="3307">User makes a request via URL.</p>
</li>
<li data-start="3308" data-end="3368">
<p data-start="3311" data-end="3368"><code data-start="3311" data-end="3322">index.php</code> (Front Controller) initializes CodeIgniter.</p>
</li>
<li data-start="3369" data-end="3436">
<p data-start="3372" data-end="3436">Router checks the URL and routes it to the correct controller.</p>
</li>
<li data-start="3437" data-end="3491">
<p data-start="3440" data-end="3491">Controller loads the necessary model(s) for data.</p>
</li>
<li data-start="3492" data-end="3534">
<p data-start="3495" data-end="3534">Model fetches data from the database.</p>
</li>
<li data-start="3535" data-end="3574">
<p data-start="3538" data-end="3574">Controller sends data to the view.</p>
</li>
<li data-start="3575" data-end="3620">
<p data-start="3578" data-end="3620">View formats the data into an HTML page.</p>
</li>
<li data-start="3621" data-end="3672">
<p data-start="3624" data-end="3672">Browser displays the final output to the user.</p>
</li>
</ol>
<hr data-start="3674" data-end="3677" />
<h2 data-start="3679" data-end="3727">🚀 Why Understanding Workflow is Important?</h2>
<ul data-start="3728" data-end="3907">
<li data-start="3728" data-end="3758">
<p data-start="3730" data-end="3758">Helps in debugging issues.</p>
</li>
<li data-start="3759" data-end="3809">
<p data-start="3761" data-end="3809">Makes application development more structured.</p>
</li>
<li data-start="3810" data-end="3862">
<p data-start="3812" data-end="3862">Improves efficiency when building scalable apps.</p>
</li>
<li data-start="3863" data-end="3907">
<p data-start="3865" data-end="3907">Provides clarity for team collaboration.</p>
</li>
</ul>
<hr data-start="3909" data-end="3912" />
<h2 data-start="3914" data-end="3929">Conclusion</h2>
<p data-start="3930" data-end="4139">The <strong data-start="3934" data-end="3975">workflow of a CodeIgniter application</strong> is designed to be <strong data-start="3994" data-end="4026">simple, fast, and structured</strong>. Every request follows the same cycle &mdash; <strong data-start="4067" data-end="4136">Front Controller &rarr; Routing &rarr; Controller &rarr; Model &rarr; View &rarr; Response</strong>.</p>
<p data-start="4141" data-end="4252">Understanding this flow is essential for writing clean, efficient, and maintainable CodeIgniter applications.</p>

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