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| <td><h1>Code Igniter User Guide Version 1.4.0</h1></td> | |
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| <a href="http://www.codeigniter.com/">Code Igniter Home</a> › | |
| <a href="../index.html">User Guide Home</a> › | |
| Controllers | |
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| <h1>Controllers</h1> | |
| <p>Controllers are the heart of your application, as they determine how HTTP requests should be handled.</p> | |
| <ul> | |
| <li><a href="#what">What is a Controller?</a></li> | |
| <li><a href="#hello">Hello World</a></li> | |
| <li><a href="#functions">Functions</a></li> | |
| <li><a href="#private">Private Functions</a></li> | |
| <li><a href="#default">Defining a Default Controller</a></li> | |
| <li><a href="#constructors">Class Constructors</a></li> | |
| <li><a href="#reserved">Reserved Function Names</a></li> | |
| </ul> | |
| <a name="what"></a> | |
| <h2>What is a Controller?</h2> | |
| <p><dfn>A Controller is simply a class file that is named in a way that can be associated with a URI.</dfn></p> | |
| <p>Consider this URI:</p> | |
| <code>www.your-site.com/index.php/<var>blog</var>/</code> | |
| <p>In the above example, Code Igniter would attempt to find a controller named <dfn>blog.php</dfn> and load it.</p> | |
| <p><strong>When a controller's name matches the first segment of a URI, it will be loaded.</strong></p> | |
| <a name="hello"></a> | |
| <h2>Let's try it: Hello World!</h2> | |
| <p>Let's create a simple controller so you can see it in action. Using your text editor, create a file called <dfn>blog.php</dfn>, and put the following code in it:</p> | |
| <textarea class="textarea" style="width:100%" cols="50" rows="10"> | |
| <?php | |
| class Blog extends Controller { | |
| function index() | |
| { | |
| echo 'Hello World!'; | |
| } | |
| } | |
| ?> | |
| </textarea> | |
| <p>Then save the file to your <dfn>application/controllers/</dfn> folder.</p> | |
| <p>Now visit the your site using a URL similar to this:</p> | |
| <code>www.your-site.com/index.php/<var>blog</var>/</code> | |
| <p>If you did it right, you should see <samp>Hello World!</samp>.</p> | |
| <p>Note: Class names must start with an uppercase letter. In other words, this is valid: | |
| <code><?php<br /> | |
| class <var>Blog</var> extends Controller {<br /> | |
| <br /> | |
| }<br /> | |
| ?></code> | |
| <p>This is <strong>not</strong> valid:</p> | |
| <code><?php<br /> | |
| class <var>blog</var> extends Controller {<br /> | |
| <br /> | |
| }<br /> | |
| ?></code> | |
| <p>Also, always make sure your controller <dfn>extends</dfn> the parent controller class so that it can inherit all its functions.</p> | |
| <a name="functions"></a> | |
| <h2>Functions</h2> | |
| <p>In the above example the function name is <dfn>index()</dfn>. The "index" function is always loaded by default if the | |
| <strong>second segment</strong> of the URI is empty. Another way to show your "Hello World" message would be this:</p> | |
| <code>www.your-site.com/index.php/<var>blog</var>/<samp>index</samp>/</code> | |
| <p><strong>The second segment of the URI determines which function in the controller gets called.</strong></p> | |
| <p>Let's try it. Add a new function to your controller:</p> | |
| <textarea class="textarea" style="width:100%" cols="50" rows="15"> | |
| <?php | |
| class Blog extends Controller { | |
| function index() | |
| { | |
| echo 'Hello World!'; | |
| } | |
| function comments() | |
| { | |
| echo 'Look at this!'; | |
| } | |
| } | |
| ?> | |
| </textarea> | |
| <p>Now load the following URL to see the <dfn>comment</dfn> function:</p> | |
| <code>www.your-site.com/index.php/<var>blog</var>/<samp>comments</samp>/</code> | |
| <p>You should see your new message.</p> | |
| <a name="private"></a> | |
| <h2>Private Functions</h2> | |
| <p>In some cases you may not want certain functions accessible publicly. To make a function private, simply add an | |
| underscore as the name prefix and it will not be served via a URL request. For example, if you were to have a function like this:</p> | |
| <code> | |
| function _utility()<br /> | |
| {<br /> | |
| // some code<br /> | |
| }</code> | |
| <p>Trying to access it via the URL, like this, will not work:</p> | |
| <code>www.your-site.com/index.php/<var>blog</var>/<samp>_utility</samp>/</code> | |
| <a name="default"></a> | |
| <h2>Defining a Default Controller</h2> | |
| <p>Code Igniter can be told to load a default controller when a URI is not present, | |
| as will be the case when only your site root URL is requested. To specify a default controller, open | |
| your <dfn>application/config/routes.php</dfn> file and set this variable:</p> | |
| <code>$route['default_controller'] = '<var>Blog</var>';</code> | |
| <p>Where <var>Blog</var> is the name of the controller class you want used. If you now load your main index.php file without | |
| specifying any URI segments you'll see your Hello World message by default.</p> | |
| <a name="constructors"></a> | |
| <h2>Class Constructors</h2> | |
| <p>If you intend to use a constructor in any of your Controllers, you <strong>MUST</strong> place the following line of code in it:</p> | |
| <code>parent::Controller();</code> | |
| <p>The reason this line is necessary is because your local constructor will be overriding the one in the parent controller class so we need to manually call it.</p> | |
| <p>If you are not familliar with constructors, in PHP 4, a <em>constructor</em> is simply a function that has the exact same name as the class:</p> | |
| <code> | |
| <?php<br /> | |
| class <kbd>Blog</kbd> extends Controller {<br /> | |
| <br /> | |
| function <kbd>Blog()</kbd><br /> | |
| {<br /> | |
| <var>parent::Controller();</var><br /> | |
| }<br /> | |
| }<br /> | |
| ?></code> | |
| <p>In PHP 5, constructors use the following syntax:</p> | |
| <code> | |
| <?php<br /> | |
| class <kbd>Blog</kbd> extends Controller {<br /> | |
| <br /> | |
| function <kbd>__construct()</kbd><br /> | |
| {<br /> | |
| <var>parent::Controller();</var><br /> | |
| }<br /> | |
| }<br /> | |
| ?></code> | |
| <p>Constructors are useful if you need to set some default values, or run a default process when your class is instantiated. | |
| Constructors can't return a value, but they can do some default work.</p> | |
| <a name="reserved"></a> | |
| <h2>Reserved Function Names</h2> | |
| <p>Since your controller classes will extend the main application controller you | |
| must be careful not to name your functions identically to the ones used by that class, otherwise your local functions | |
| will override them. The following | |
| is a list of reserved names. Do not name your controller functions any of these:</p> | |
| <ul> | |
| <li>Controller</li> | |
| <li>CI_Base</li> | |
| <li>_ci_autoload</li> | |
| <li>_ci_autoloader</li> | |
| <li>_ci_assign_core</li> | |
| <li>_ci_initialize</li> | |
| <li>_ci_init_database</li> | |
| <li>_ci_init_scaffolding</li> | |
| <li>_ci_is_loaded</li> | |
| <li>_ci_load</li> | |
| <li>_ci_scaffolding</li> | |
| <li>_ci_set_view_path</li> | |
| </ul> | |
| <p><br />If you are running PHP 4 there are some additional reserved names. These ONLY apply if you are running PHP 4.</p> | |
| <ul> | |
| <li>CI_Loader</li> | |
| <li>config</li> | |
| <li>database</li> | |
| <li>file</li> | |
| <li>helper</li> | |
| <li>helpers</li> | |
| <li>language</li> | |
| <li>library</li> | |
| <li>plugin</li> | |
| <li>plugins</li> | |
| <li>scaffolding</li> | |
| <li>script</li> | |
| <li>view</li> | |
| <li>vars</li> | |
| </ul> | |
| <h2>That's it!</h2> | |
| <p>That, in a nutshell, is all there is to know about controllers.</p> | |
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