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Derek Jones8917af72010-03-05 12:41:45 -0600[diff] [blame]31<td><h1>CodeIgniter User Guide Version 2.0.0</h1></td>
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]32<td id="breadcrumb_right"><a href="../toc.html">Table of Contents Page</a></td>
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43<a href="http://codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;
44<a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;
45Controllers
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47<td id="searchbox"><form method="get" action="http://www.google.com/search"><input type="hidden" name="as_sitesearch" id="as_sitesearch" value="codeigniter.com/user_guide/" />Search User Guide&nbsp; <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" />&nbsp;<input type="submit" class="submit" name="sa" value="Go" /></form></td>
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56<div id="content">
57
58<h1>Controllers</h1>
59
60<p>Controllers are the heart of your application, as they determine how HTTP requests should be handled.</p>
61
62
63<ul>
64<li><a href="#what">What is a Controller?</a></li>
65<li><a href="#hello">Hello World</a></li>
66<li><a href="#functions">Functions</a></li>
67<li><a href="#passinguri">Passing URI Segments to Your Functions</a></li>
68<li><a href="#default">Defining a Default Controller</a></li>
69<li><a href="#remapping">Remapping Function Calls</a></li>
70<li><a href="#output">Controlling Output Data</a></li>
71<li><a href="#private">Private Functions</a></li>
72<li><a href="#subfolders">Organizing Controllers into Sub-folders</a></li>
73<li><a href="#constructors">Class Constructors</a></li>
74<li><a href="#reserved">Reserved Function Names</a></li>
75</ul>
76
77
78<a name="what"></a>
79<h2>What is a Controller?</h2>
80
81<p><dfn>A Controller is simply a class file that is named in a way that can be associated with a URI.</dfn></p>
82
83<p>Consider this URI:</p>
84
85<code>example.com/index.php/<var>blog</var>/</code>
86
87<p>In the above example, CodeIgniter would attempt to find a controller named <dfn>blog.php</dfn> and load it.</p>
88
89<p><strong>When a controller's name matches the first segment of a URI, it will be loaded.</strong></p>
90
91<a name="hello"></a>
92<h2>Let's try it:&nbsp; Hello World!</h2>
93
94<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>
95
96
97<textarea class="textarea" style="width:100%" cols="50" rows="10">
Derek Allard4b6d4932008-12-07 17:04:56 +0000[diff] [blame]98&lt;?php
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]99class Blog extends Controller {
100
101 function index()
102 {
103 echo 'Hello World!';
104 }
105}
Derek Allard4b6d4932008-12-07 17:04:56 +0000[diff] [blame]106?&gt;
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]107</textarea>
108
109
110
111<p>Then save the file to your <dfn>application/controllers/</dfn> folder.</p>
112
113<p>Now visit the your site using a URL similar to this:</p>
114
115<code>example.com/index.php/<var>blog</var>/</code>
116
117<p>If you did it right, you should see <samp>Hello World!</samp>.</p>
118
119<p>Note: Class names must start with an uppercase letter. In other words, this is valid:</p>
120
121<code>&lt;?php<br />
122class <var>Blog</var> extends Controller {<br />
123<br />
124}<br />
125?&gt;</code>
126
127<p>This is <strong>not</strong> valid:</p>
128
129<code>&lt;?php<br />
130class <var>blog</var> extends Controller {<br />
131<br />
132}<br />
133?&gt;</code>
134
135<p>Also, always make sure your controller <dfn>extends</dfn> the parent controller class so that it can inherit all its functions.</p>
136
137
138
139<a name="functions"></a>
140<h2>Functions</h2>
141
142<p>In the above example the function name is <dfn>index()</dfn>. The "index" function is always loaded by default if the
143<strong>second segment</strong> of the URI is empty. Another way to show your "Hello World" message would be this:</p>
144
145<code>example.com/index.php/<var>blog</var>/<samp>index</samp>/</code>
146
147<p><strong>The second segment of the URI determines which function in the controller gets called.</strong></p>
148
149<p>Let's try it. Add a new function to your controller:</p>
150
151
152<textarea class="textarea" style="width:100%" cols="50" rows="15">
Derek Allard4b6d4932008-12-07 17:04:56 +0000[diff] [blame]153&lt;?php
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]154class Blog extends Controller {
155
156 function index()
157 {
158 echo 'Hello World!';
159 }
160
161 function comments()
162 {
163 echo 'Look at this!';
164 }
165}
Derek Allard4b6d4932008-12-07 17:04:56 +0000[diff] [blame]166?&gt;
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]167</textarea>
168
169<p>Now load the following URL to see the <dfn>comment</dfn> function:</p>
170
171<code>example.com/index.php/<var>blog</var>/<samp>comments</samp>/</code>
172
173<p>You should see your new message.</p>
174
175<a name="passinguri"></a>
176<h2>Passing URI Segments to your Functions</h2>
177
178<p>If your URI contains more then two segments they will be passed to your function as parameters.</p>
179
180<p>For example, lets say you have a URI like this:</p>
181
182<code>example.com/index.php/<var>products</var>/<samp>shoes</samp>/<kbd>sandals</kbd>/<dfn>123</dfn></code>
183
184<p>Your function will be passed URI segments 3 and 4 ("sandals" and "123"):</p>
185
186<code>
187&lt;?php<br />
188class Products extends Controller {<br />
189<br />
190&nbsp;&nbsp;&nbsp;&nbsp;function shoes($sandals, $id)<br />
191&nbsp;&nbsp;&nbsp;&nbsp;{<br />
192&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo $sandals;<br />
193&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo $id;<br />
194&nbsp;&nbsp;&nbsp;&nbsp;}<br />
195}<br />
196?&gt;
197</code>
198
199<p class="important"><strong>Important:</strong>&nbsp; If you are using the <a href="routing.html">URI Routing</a> feature, the segments
200passed to your function will be the re-routed ones.</p>
201
202
203<a name="default"></a>
204<h2>Defining a Default Controller</h2>
205
206<p>CodeIgniter can be told to load a default controller when a URI is not present,
207as will be the case when only your site root URL is requested. To specify a default controller, open
208your <dfn>application/config/routes.php</dfn> file and set this variable:</p>
209
210<code>$route['default_controller'] = '<var>Blog</var>';</code>
211
212<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
213specifying any URI segments you'll see your Hello World message by default.</p>
214
215
216
217<a name="remapping"></a>
218<h2>Remapping Function Calls</h2>
219
220<p>As noted above, the second segment of the URI typically determines which function in the controller gets called.
221CodeIgniter permits you to override this behavior through the use of the <kbd>_remap()</kbd> function:</p>
222
223<code>function _remap()<br />
224{<br />
225&nbsp;&nbsp;&nbsp;&nbsp;// Some code here...<br />
226}</code>
227
228<p class="important"><strong>Important:</strong>&nbsp; If your controller contains a function named <kbd>_remap()</kbd>, it will <strong>always</strong>
229get called regardless of what your URI contains. It overrides the normal behavior in which the URI determines which function is called,
230allowing you to define your own function routing rules.</p>
231
232<p>The overridden function call (typically the second segment of the URI) will be passed as a parameter the <kbd>_remap()</kbd> function:</p>
233
234<code>function _remap(<var>$method</var>)<br />
235{<br />
236&nbsp;&nbsp;&nbsp;&nbsp;if ($method == 'some_method')<br />
237&nbsp;&nbsp;&nbsp;&nbsp;{<br />
238&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$this->$method();<br />
239&nbsp;&nbsp;&nbsp;&nbsp;}<br />
240&nbsp;&nbsp;&nbsp;&nbsp;else<br />
241&nbsp;&nbsp;&nbsp;&nbsp;{<br />
242&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$this->default_method();<br />
243&nbsp;&nbsp;&nbsp;&nbsp;}<br />
244}</code>
245
246
247
248
249
250<a name="output"></a>
251<h2>Processing Output</h2>
252
253<p>CodeIgniter has an output class that takes care of sending your final rendered data to the web browser automatically. More information on this can be found in the
254<a href="views.html">Views</a> and <a href="../libraries/output.html">Output class</a> pages. In some cases, however, you might want to
255post-process the finalized data in some way and send it to the browser yourself. CodeIgniter permits you to
256add a function named <dfn>_output()</dfn> to your controller that will receive the finalized output data.</p>
257
258<p><strong>Important:</strong>&nbsp; If your controller contains a function named <kbd>_output()</kbd>, it will <strong>always</strong>
259be called by the output class instead of echoing the finalized data directly. The first parameter of the function will contain the finalized output.</p>
260
261<p>Here is an example:</p>
262
263<code>
264function _output($output)<br />
265{<br />
266&nbsp;&nbsp;&nbsp;&nbsp;echo $output;<br />
267}</code>
268
269<p class="important">Please note that your <dfn>_output()</dfn> function will receive the data in its finalized state. Benchmark and memory usage data will be rendered,
270cache files written (if you have caching enabled), and headers will be sent (if you use that <a href="../libraries/output.html">feature</a>)
Derek Jonesd7633492010-09-28 13:14:57 -0500[diff] [blame]271before it is handed off to the _output() function.<br />
272<br />
273To have your controller's output cached properly, its <dfn>_output()</dfn> method can use:<br />
274
275<code>if ($this-&gt;output-&gt;cache_expiration &gt; 0)<br />
276{<br />
Derek Jones3351fbc2010-10-01 09:56:31 -0500[diff] [blame]277&nbsp;&nbsp;&nbsp;&nbsp;$this-&gt;output-&gt;_write_cache($output);<br />
Derek Jonesd7633492010-09-28 13:14:57 -0500[diff] [blame]278}</code>
279
280If you are using this feature the page execution timer and memory usage stats might not be perfectly accurate
Derek Allard2067d1a2008-11-13 22:59:24 +0000[diff] [blame]281since they will not take into acccount any further processing you do. For an alternate way to control output <em>before</em> any of the final processing is done, please see
282the available methods in the <a href="../libraries/output.html">Output Class</a>.</p>
283
284<a name="private"></a>
285<h2>Private Functions</h2>
286
287
288<p>In some cases you may want certain functions hidden from public access. To make a function private, simply add an
289underscore 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>
290
291<code>
292function _utility()<br />
293{<br />
294&nbsp;&nbsp;// some code<br />
295}</code>
296
297<p>Trying to access it via the URL, like this, will not work:</p>
298
299<code>example.com/index.php/<var>blog</var>/<samp>_utility</samp>/</code>
300
301
302
303<a name="subfolders"></a>
304<h2>Organizing Your Controllers into Sub-folders</h2>
305
306<p>If you are building a large application you might find it convenient to organize your controllers into sub-folders. CodeIgniter permits you to do this.</p>
307
308<p>Simply create folders within your <dfn>application/controllers</dfn> directory and place your controller classes within them.</p>
309
310<p><strong>Note:</strong>&nbsp; When using this feature the first segment of your URI must specify the folder. For example, lets say you have a controller
311located here:</p>
312
313<code>application/controllers/<kbd>products</kbd>/shoes.php</code>
314
315<p>To call the above controller your URI will look something like this:</p>
316
317<code>example.com/index.php/products/shoes/show/123</code>
318
319<p>Each of your sub-folders may contain a default controller which will be
320called if the URL contains only the sub-folder. Simply name your default controller as specified in your
321<dfn>application/config/routes.php</dfn> file</p>
322
323
324<p>CodeIgniter also permits you to remap your URIs using its <a href="routing.html">URI Routing</a> feature.</p>
325
326
327<h2><a name="constructors"></a>Class Constructors</h2>
328
329
330<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>
331
332<code>parent::Controller();</code>
333
334<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>
335
336
337<p>If you are not familiar with constructors, in PHP 4, a <em>constructor</em> is simply a function that has the exact same name as the class:</p>
338
339<code>
340&lt;?php<br />
341class <kbd>Blog</kbd> extends Controller {<br />
342<br />
343&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;function <kbd>Blog()</kbd><br />
344&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br />
345&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<var>parent::Controller();</var><br />
346&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />
347}<br />
348?&gt;</code>
349
350<p>In PHP 5, constructors use the following syntax:</p>
351
352<code>
353&lt;?php<br />
354class <kbd>Blog</kbd> extends Controller {<br />
355<br />
356&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;function <kbd>__construct()</kbd><br />
357&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br />
358&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<var>parent::Controller();</var><br />
359&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />
360}<br />
361?&gt;</code>
362
363<p>Constructors are useful if you need to set some default values, or run a default process when your class is instantiated.
364Constructors can't return a value, but they can do some default work.</p>
365
366<a name="reserved"></a>
367<h2>Reserved Function Names</h2>
368
369<p>Since your controller classes will extend the main application controller you
370must be careful not to name your functions identically to the ones used by that class, otherwise your local functions
371will override them. See <a href="reserved_names.html">Reserved Names</a> for a full list.</p>
372
373<h2>That's it!</h2>
374
375<p>That, in a nutshell, is all there is to know about controllers.</p>
376
377
378
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Derek Jonesd6d70e32010-03-29 10:10:27 -0500[diff] [blame]390<p><a href="http://codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2006-2010 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">EllisLab, Inc.</a></p>
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