CodeIgniter Home
- What is CodeIgniter?
- Features of CodeIgniter
- Advantages over other PHP frameworks
- CodeIgniter version history
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)
- Downloading & Extracting CodeIgniter
- Folder structure explained
- Setting base URL
- Configuring index.php file
- Running first application
CodeIgniter Application Architecture
- Folder structure in detail
- Application vs System folders
- Config, Controllers, Models, Views
- Helpers and Libraries placement
- User Guide access
CodeIgniter MVC Framework
- Understanding MVC flow
- Codeigniter Creating Controllers
- Creating Views
- Creating Models
- 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
- Error logging configuration
- 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
- Result handling (row(), result())
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

Folder structure in detail

Last modified on: September 7, 2025

<h1 data-start="516" data-end="561">📝 CodeIgniter Folder Structure in Detail</h1>
<h2 data-start="563" data-end="583">🔎 Introduction</h2>
<p data-start="584" data-end="806">CodeIgniter organizes your project into several <strong data-start="632" data-end="647">key folders</strong>, separating application logic from system files. Understanding the <strong data-start="715" data-end="735">folder structure</strong> is crucial for effective development, security, and maintainability.</p>
<p data-start="808" data-end="876">Here&rsquo;s a detailed breakdown of <strong data-start="839" data-end="873">CodeIgniter 4 folder structure</strong>.</p>
<hr data-start="878" data-end="881" />
<h2 data-start="883" data-end="921">📂 1. <code data-start="892" data-end="898">app/</code> (Application Folder)</h2>
<p data-start="923" data-end="989">The <strong data-start="927" data-end="941">app folder</strong> contains <strong data-start="951" data-end="986">all your project-specific files</strong>.</p>
<h3 data-start="991" data-end="1020">Subfolders and Purpose:</h3>
<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="1022" data-end="1868">
<thead data-start="1022" data-end="1053">
<tr data-start="1022" data-end="1053">
<th data-start="1022" data-end="1042" data-col-size="sm">Subfolder</th>
<th data-start="1042" data-end="1053" data-col-size="md">Purpose</th>
</tr>
</thead>
<tbody data-start="1085" data-end="1868">
<tr data-start="1085" data-end="1205">
<td data-start="1085" data-end="1104" data-col-size="sm"><code data-start="1087" data-end="1101">Controllers/</code></td>
<td data-start="1104" data-end="1205" data-col-size="md">Handle user requests and interact with models &amp; views. Example: <code data-start="1170" data-end="1180">Home.php</code> handles default pages.</td>
</tr>
<tr data-start="1206" data-end="1323">
<td data-start="1206" data-end="1225" data-col-size="sm"><code data-start="1208" data-end="1217">Models/</code></td>
<td data-start="1225" data-end="1323" data-col-size="md">Manage database interactions and business logic. Example: <code data-start="1285" data-end="1300">UserModel.php</code> retrieves user data.</td>
</tr>
<tr data-start="1324" data-end="1414">
<td data-start="1324" data-end="1343" data-col-size="sm"><code data-start="1326" data-end="1334">Views/</code></td>
<td data-start="1343" data-end="1414" data-col-size="md">Store HTML/PHP templates to render pages. Example: <code data-start="1396" data-end="1411">home_view.php</code>.</td>
</tr>
<tr data-start="1415" data-end="1505">
<td data-start="1415" data-end="1434" data-col-size="sm"><code data-start="1417" data-end="1426">Config/</code></td>
<td data-start="1434" data-end="1505" data-col-size="md">Store configuration files (database, routes, email, filters, etc.).</td>
</tr>
<tr data-start="1506" data-end="1571">
<td data-start="1506" data-end="1525" data-col-size="sm"><code data-start="1508" data-end="1518">Helpers/</code></td>
<td data-start="1525" data-end="1571" data-col-size="md">Custom helper functions to simplify tasks.</td>
</tr>
<tr data-start="1572" data-end="1655">
<td data-start="1572" data-end="1591" data-col-size="sm"><code data-start="1574" data-end="1584">Filters/</code></td>
<td data-start="1591" data-end="1655" data-col-size="md">Middleware-like functionality to process requests/responses.</td>
</tr>
<tr data-start="1656" data-end="1725">
<td data-start="1656" data-end="1675" data-col-size="sm"><code data-start="1658" data-end="1669">Language/</code></td>
<td data-start="1675" data-end="1725" data-col-size="md">Localization files for multi-language support.</td>
</tr>
<tr data-start="1726" data-end="1810">
<td data-start="1726" data-end="1745" data-col-size="sm"><code data-start="1728" data-end="1740">Libraries/</code></td>
<td data-start="1745" data-end="1810" data-col-size="md">Custom libraries for reusable code across controllers/models.</td>
</tr>
<tr data-start="1811" data-end="1868">
<td data-start="1811" data-end="1830" data-col-size="sm"><code data-start="1813" data-end="1824">Commands/</code></td>
<td data-start="1830" data-end="1868" data-col-size="md">Custom CLI commands using <code data-start="1858" data-end="1865">spark</code>.</td>
</tr>
</tbody>
</table>
</div>
</div>
<p data-start="1870" data-end="1884"><strong data-start="1870" data-end="1882">Example:</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>app/Controllers/Home.php
app/Models/ProductModel.php
app/Views/product_view.php
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="1977" data-end="1980" />
<h2 data-start="1982" data-end="2018">📂 2. <code data-start="1991" data-end="2000">public/</code> (Public Folder)</h2>
<ul data-start="2020" data-end="2197">
<li data-start="2020" data-end="2073">
<p data-start="2022" data-end="2073"><strong data-start="2022" data-end="2056">Entry point of the application</strong> (<code data-start="2058" data-end="2069">index.php</code>).</p>
</li>
<li data-start="2074" data-end="2120">
<p data-start="2076" data-end="2120">Stores <strong data-start="2083" data-end="2100">public assets</strong>: CSS, JS, images.</p>
</li>
<li data-start="2121" data-end="2197">
<p data-start="2123" data-end="2197">Ensures security by keeping system and app folders outside the web root.</p>
</li>
</ul>
<p data-start="2199" data-end="2223"><strong data-start="2199" data-end="2221">Example Structure:</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>public/
├── index.php
├── css/
├── js/
└── images/
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2284" data-end="2287" />
<h2 data-start="2289" data-end="2326">📂 3. <code data-start="2298" data-end="2307">system/</code> (Framework Core)</h2>
<ul data-start="2328" data-end="2531">
<li data-start="2328" data-end="2382">
<p data-start="2330" data-end="2382">Contains <strong data-start="2339" data-end="2365">CodeIgniter core files</strong> and libraries.</p>
</li>
<li data-start="2383" data-end="2455">
<p data-start="2385" data-end="2455">Handles routing, request processing, database interaction, and more.</p>
</li>
<li data-start="2456" data-end="2531">
<p data-start="2458" data-end="2531"><strong data-start="2458" data-end="2475">Do not modify</strong> &mdash; changes may break the framework or prevent updates.</p>
</li>
</ul>
<p data-start="2533" data-end="2578"><strong data-start="2533" data-end="2576">Example Libraries Inside System Folder:</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>system/
├── CodeIgniter.php
├── Core/
├── Database/
├── View/
└── Router.php
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="2665" data-end="2668" />
<h2 data-start="2670" data-end="2710">📂 4. <code data-start="2679" data-end="2690">writable/</code> (Writable Folder)</h2>
<ul data-start="2712" data-end="2962">
<li data-start="2712" data-end="2764">
<p data-start="2714" data-end="2764">Stores data that requires <strong data-start="2740" data-end="2761">write permissions</strong>.</p>
</li>
<li data-start="2765" data-end="2962">
<p data-start="2767" data-end="2780">Subfolders:</p>
<ul data-start="2783" data-end="2962">
<li data-start="2783" data-end="2832">
<p data-start="2785" data-end="2832"><code data-start="2785" data-end="2793">cache/</code> &rarr; Cache data for faster performance.</p>
</li>
<li data-start="2835" data-end="2880">
<p data-start="2837" data-end="2880"><code data-start="2837" data-end="2844">logs/</code> &rarr; Application logs for debugging.</p>
</li>
<li data-start="2883" data-end="2922">
<p data-start="2885" data-end="2922"><code data-start="2885" data-end="2896">sessions/</code> &rarr; Session data storage.</p>
</li>
<li data-start="2925" data-end="2962">
<p data-start="2927" data-end="2962"><code data-start="2927" data-end="2937">uploads/</code> &rarr; User-uploaded files.</p>
</li>
</ul>
</li>
</ul>
<p data-start="2964" data-end="3055"><strong data-start="2964" data-end="2973">Note:</strong> Set proper permissions (<code data-start="2998" data-end="3022">chmod -R 777 writable/</code>) for development environments.</p>
<hr data-start="3057" data-end="3060" />
<h2 data-start="3062" data-end="3081">📂 5. <code data-start="3071" data-end="3079">tests/</code></h2>
<ul data-start="3083" data-end="3197">
<li data-start="3083" data-end="3137">
<p data-start="3085" data-end="3137">Contains <strong data-start="3094" data-end="3120">unit and feature tests</strong> using PHPUnit.</p>
</li>
<li data-start="3138" data-end="3197">
<p data-start="3140" data-end="3197">Helps maintain code quality by running automated tests.</p>
</li>
</ul>
<p data-start="3199" data-end="3213"><strong data-start="3199" data-end="3211">Example:</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>tests/
├── Unit/
│   └── ProductTest.php
└── Feature/
    └── UserControllerTest.php
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="3308" data-end="3311" />
<h2 data-start="3313" data-end="3333">📂 6. <code data-start="3322" data-end="3331">vendor/</code></h2>
<ul data-start="3335" data-end="3501">
<li data-start="3335" data-end="3393">
<p data-start="3337" data-end="3393">Created when installing CodeIgniter with <strong data-start="3378" data-end="3390">Composer</strong>.</p>
</li>
<li data-start="3394" data-end="3448">
<p data-start="3396" data-end="3448">Stores <strong data-start="3403" data-end="3428">third-party libraries</strong> and dependencies.</p>
</li>
<li data-start="3449" data-end="3501">
<p data-start="3451" data-end="3501">Contains <code data-start="3460" data-end="3474">autoload.php</code> for autoloading classes.</p>
</li>
</ul>
<p data-start="3503" data-end="3517"><strong data-start="3503" data-end="3515">Example:</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>vendor/
├── codeigniter4/
└── composer/
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="3567" data-end="3570" />
<h2 data-start="3572" data-end="3589">📄 7. <code data-start="3581" data-end="3587">.env</code></h2>
<ul data-start="3591" data-end="3791">
<li data-start="3591" data-end="3725">
<p data-start="3593" data-end="3636">Stores <strong data-start="3600" data-end="3633">environment-specific settings</strong>:</p>
<ul data-start="3639" data-end="3725">
<li data-start="3639" data-end="3663">
<p data-start="3641" data-end="3663">Database credentials</p>
</li>
<li data-start="3666" data-end="3710">
<p data-start="3668" data-end="3710">App environment (development/production)</p>
</li>
<li data-start="3713" data-end="3725">
<p data-start="3715" data-end="3725">Base URL</p>
</li>
</ul>
</li>
<li data-start="3726" data-end="3791">
<p data-start="3728" data-end="3791">Recommended to <strong data-start="3743" data-end="3775">keep outside version control</strong> for security.</p>
</li>
</ul>
<p data-start="3793" data-end="3814"><strong data-start="3793" data-end="3812">Example <code data-start="3803" data-end="3809">.env</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>app.baseURL = 'http://localhost:8080/'
database.default.hostname = localhost
database.default.database = ci_db
database.default.username = root
database.default.password = ''
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="4002" data-end="4005" />
<h2 data-start="4007" data-end="4033">📄 8. <code data-start="4016" data-end="4031">composer.json</code></h2>
<ul data-start="4035" data-end="4150">
<li data-start="4035" data-end="4092">
<p data-start="4037" data-end="4092">Defines project dependencies when using <strong data-start="4077" data-end="4089">Composer</strong>.</p>
</li>
<li data-start="4093" data-end="4150">
<p data-start="4095" data-end="4150">Lists required packages, scripts, and autoload rules.</p>
</li>
</ul>
<hr data-start="4152" data-end="4155" />
<h2 data-start="4157" data-end="4186">📄 9. <code data-start="4166" data-end="4173">spark</code> (CLI Tool)</h2>
<ul data-start="4188" data-end="4306">
<li data-start="4188" data-end="4235">
<p data-start="4190" data-end="4235"><strong data-start="4190" data-end="4216">Command-line interface</strong> for CodeIgniter.</p>
</li>
<li data-start="4236" data-end="4306">
<p data-start="4238" data-end="4306">Used to run server, create controllers/models, and run migrations.</p>
</li>
</ul>
<p data-start="4308" data-end="4331"><strong data-start="4308" data-end="4329">Example Commands:</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>php spark serve           # Start development server
php spark make:controller User  # Generate a controller
php spark migrate         # Run database migrations
</code></pre>
</div>
</div>
</div>
</div>
<hr data-start="4506" data-end="4509" />
<h2 data-start="4511" data-end="4529">🎯 Conclusion</h2>
<p data-start="4531" data-end="4659">The <strong data-start="4535" data-end="4567">CodeIgniter folder structure</strong> is designed to separate <strong data-start="4592" data-end="4645">application code, system files, and public assets</strong>, making it:</p>
<ul data-start="4661" data-end="4871">
<li data-start="4661" data-end="4708">
<p data-start="4663" data-end="4708"><strong data-start="4663" data-end="4673">Secure</strong> &rarr; system files outside web root.</p>
</li>
<li data-start="4709" data-end="4760">
<p data-start="4711" data-end="4760"><strong data-start="4711" data-end="4724">Organized</strong> &rarr; MVC pattern separates concerns.</p>
</li>
<li data-start="4761" data-end="4817">
<p data-start="4763" data-end="4817"><strong data-start="4763" data-end="4775">Scalable</strong> &rarr; Easy to add features without clutter.</p>
</li>
<li data-start="4818" data-end="4871">
<p data-start="4820" data-end="4871"><strong data-start="4820" data-end="4836">Maintainable</strong> &rarr; Clear folder responsibilities.</p>
</li>
</ul>
<p data-start="4873" data-end="4982">Understanding each folder and its purpose is crucial for <strong data-start="4930" data-end="4979">efficient development and project maintenance</strong>.</p>

Web Technology View More