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Derek Jonesfd93d222008-05-06 15:18:50 +0000[diff] [blame^]5<title>Creating Libraries : CodeIgniter User Guide</title>
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45Creating Libraries
46</td>
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56<div id="content">
57
58<h1>Creating Libraries</h1>
59
60<p>When we use the term "Libraries" we are normally referring to the classes that are located in the <kbd>libraries</kbd>
admine334c472006-10-21 19:44:22 +0000[diff] [blame]61directory and described in the Class Reference of this user guide. In this case, however, we will instead describe how you can create
62your own libraries within your <dfn>application/libraries</dfn> directory in order to maintain separation between your local resources
admin33de9a12006-09-28 06:50:16 +0000[diff] [blame]63and the global framework resources.</p>
64
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]65<p>As an added bonus, CodeIgniter permits your libraries to <kbd>extend</kbd> native classes if you simply need to add some functionality
Derek Allardc6441282007-07-04 23:54:32 +0000[diff] [blame]66to an existing library. Or you can even replace native libraries just by placing identically named versions in your <dfn>application/libraries</dfn> folder.</p>
admin33de9a12006-09-28 06:50:16 +0000[diff] [blame]67
68<p>In summary:</p>
69
70<ul>
71<li>You can create entirely new libraries.</li>
72<li>You can extend native libraries.</li>
73<li>You can replace native libraries.</li>
74</ul>
75
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]76<p>The page below explains these three concepts in detail.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]77
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]78<p class="important"><strong>Note:</strong> The Database classes can not be extended or replaced with your own classes,
Derek Jones2e44e0b2008-02-13 03:59:34 +0000[diff] [blame]79nor can the Loader class in PHP 4. All other classes are able to be replaced/extended.</p>
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]80
81
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]82<h2>Storage</h2>
83
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]84<p>Your library classes should be placed within your <dfn>application/libraries</dfn> folder, as this is where CodeIgniter will look for them when
admin33de9a12006-09-28 06:50:16 +0000[diff] [blame]85they are initialized.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]86
87
88<h2>Naming Conventions</h2>
89
90<ul>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]91<li>File names must be capitalized. For example:&nbsp; <dfn>Myclass.php</dfn></li>
92<li>Class declarations must be capitalized. For example:&nbsp; <kbd>class Myclass</kbd></li>
93<li>Class names and file names must match.</li>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]94</ul>
95
96
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]97<h2>The Class File</h2>
98
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]99<p>Classes should have this basic prototype (Note: We are using the name <kbd>Someclass</kbd> purely as an example):</p>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]100
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]101<code>&lt;?php if (!defined('BASEPATH')) exit('No direct script access allowed');
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]102<br /><br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]103class Someclass {<br />
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]104<br />
105&nbsp;&nbsp;&nbsp;&nbsp;function some_function()<br />
106&nbsp;&nbsp;&nbsp;&nbsp;{<br />
107&nbsp;&nbsp;&nbsp;&nbsp;}<br />
108}<br /><br />
109?&gt;</code>
110
111
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]112<h2>Using Your Class</h2>
113
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]114<p>From within any of your <a href="controllers.html">Controller</a> functions you can initialize your class using the standard:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]115
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]116<code>$this->load->library('<kbd>someclass</kbd>');</code>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]117
admine334c472006-10-21 19:44:22 +0000[diff] [blame]118<p>Where <em>someclass</em> is the file name, without the ".php" file extension. You can submit the file name capitalized or lower case.
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]119CodeIgniter doesn't care.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]120
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]121<p>Once loaded you can access your class using the <kbd>lower case</kbd> version:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]122
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]123<code>$this-><kbd>someclass</kbd>->some_function();&nbsp; // Object instances will always be lower case
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]124</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]125
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]126
127
128<h2>Passing Parameters When Initializing Your Class</h2>
129
admine334c472006-10-21 19:44:22 +0000[diff] [blame]130<p>In the library loading function you can dynamically pass data via the second parameter and it will be passed to your class
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]131constructor:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]132
133<code>
134$params = array('type' => 'large', 'color' => 'red');<br />
135<br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]136$this->load->library('Someclass', <kbd>$params</kbd>);</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]137
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]138<p>If you use this feature you must set up your class constructor to expect data:</p>
139
140<code>&lt;?php if (!defined('BASEPATH')) exit('No direct script access allowed');<br />
141<br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]142class Someclass {<br />
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]143<br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]144&nbsp;&nbsp;&nbsp;&nbsp;function Someclass($params)<br />
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]145&nbsp;&nbsp;&nbsp;&nbsp;{<br />
146&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Do something with $params<br />
147&nbsp;&nbsp;&nbsp;&nbsp;}<br />
148}<br /><br />
149?&gt;</code>
150
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]151<p class="important">You can also pass parameters stored in a config file. Simply create a config file named identically to the class <kbd>file name</kbd>
152and store it in your <dfn>application/config/</dfn> folder. Note that if you dynamically pass parameters as described above,
153the config file option will not be available.</p>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]154
155
156
157
158
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]159
160
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]161<h2>Utilizing CodeIgniter Resources within Your Library</h2>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]162
163
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]164<p>To access CodeIgniter's native resources within your library use the <kbd>get_instance()</kbd> function.
165This function returns the CodeIgniter super object.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]166
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]167<p>Normally from within your controller functions you will call any of the available CodeIgniter functions using the <kbd>$this</kbd> construct:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]168
169<code>
170<strong>$this</strong>->load->helper('url');<br />
171<strong>$this</strong>->load->library('session');<br />
172<strong>$this</strong>->config->item('base_url');<br />
173etc.
174</code>
175
admine334c472006-10-21 19:44:22 +0000[diff] [blame]176<p><kbd>$this</kbd>, however, only works directly within your controllers, your models, or your views.
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]177If you would like to use CodeIgniter's classes from within your own custom classes you can do so as follows:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]178
179
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]180<p>First, assign the CodeIgniter object to a variable:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]181
Derek Allardce66d152008-03-04 20:55:55 +0000[diff] [blame]182<code>$CI =&amp; get_instance();</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]183
184<p>Once you've assigned the object to a variable, you'll use that variable <em>instead</em> of <kbd>$this</kbd>:</p>
185
186<code>
Derek Allardce66d152008-03-04 20:55:55 +0000[diff] [blame]187$CI =&amp; get_instance();<br />
188<br />
admin88a8ad12006-10-07 03:16:32 +0000[diff] [blame]189$CI->load->helper('url');<br />
190$CI->load->library('session');<br />
191$CI->config->item('base_url');<br />
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]192etc.
193</code>
194
195<p class="important"><strong>Note:</strong> You'll notice that the above get_instance() function is being passed by reference:
196<br /><br />
Derek Allardce66d152008-03-04 20:55:55 +0000[diff] [blame]197<var>$CI =&amp; get_instance();</var>
198<br />
199<br />
Rick Ellis1f852632007-06-09 00:25:57 +0000[diff] [blame]200<kbd>This is very important.</kbd> Assigning by reference allows you to use the original CodeIgniter object rather than creating a copy of it.
201<br /><br />
202<kbd>Also, please note:</kbd> If you are running PHP 4 it's usually best to avoid calling <dfn>get_instance()</dfn>
203from within your class constructors. PHP 4 has trouble referencing the CI super object within application constructors
204since objects do not exist until the class is fully instantiated.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]205
206
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]207<h2>Replacing Native Libraries with Your Versions</h2>
208
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]209<p>Simply by naming your class files identically to a native library will cause CodeIgniter to use it instead of the native one. To use this
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]210feature you must name the file and the class declaration exactly the same as the native library. For example, to replace the native <kbd>Email</kbd> library
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]211you'll create a file named <dfn>application/libraries/Email.php</dfn>, and declare your class with:</p>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]212
213<code>
214class CI_Email {<br /><br />
215
216}</code>
217
218<p>Note that most native classes are prefixed with <kbd>CI_</kbd>.</p>
219
220<p>To load your library you'll see the standard loading function:</p>
221
222<code>$this->load->library('<kbd>email</kbd>');</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]223
Derek Allard7a1f5162007-01-27 18:02:09 +0000[diff] [blame]224<p class="important"><strong>Note:</strong> At this time the Database classes can not be replaced with your own versions.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]225
226
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]227<h2>Extending Native Libraries</h2>
228
229<p>If all you need to do is add some functionality to an existing library - perhaps add a function or two - then
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]230it's overkill to replace the entire library with your version. In this case it's better to simply extend the class.
231Extending a class is nearly identical to replacing a class with a couple exceptions:</p>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]232
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]233<ul>
234<li>The class declaration must extend the parent class.</li>
admine334c472006-10-21 19:44:22 +0000[diff] [blame]235<li>Your new class name and filename must be prefixed with <kbd>MY_</kbd> (this item is configurable. See below.).</li>
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]236</ul>
237
238<p>For example, to extend the native <kbd>Email</kbd> class you'll create a file named <dfn>application/libraries/</dfn><kbd>MY_Email.php</kbd>, and declare your class with:</p>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]239
240<code>
241class MY_Email extends CI_Email {<br /><br />
242
243}</code>
244
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]245<p>Note: If you need to use a constructor in your class make sure you extend the parent constructor:</p>
246
247
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]248<code>
249class MY_Email extends CI_Email {<br />
250<br />
251&nbsp;&nbsp;&nbsp;&nbsp;function My_Email()<br />
252&nbsp;&nbsp;&nbsp;&nbsp;{<br />
253&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;parent::CI_Email();<br />
254&nbsp;&nbsp;&nbsp;&nbsp;}<br />
255}</code>
256
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]257
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]258<h3>Loading Your Sub-class</h3>
259
260<p>To load your sub-class you'll use the standard syntax normally used. DO NOT include your prefix. For example,
261to load the example above, which extends the Email class, you will use:</p>
262
263<code>$this->load->library('<kbd>email</kbd>');</code>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]264
admine334c472006-10-21 19:44:22 +0000[diff] [blame]265<p>Once loaded you will use the class variable as you normally would for the class you are extending. In the case of
Derek Allardc6441282007-07-04 23:54:32 +0000[diff] [blame]266the email class all calls will use:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]267
268
admincf493902006-10-10 07:12:31 +0000[diff] [blame]269<code>$this-><kbd>email</kbd>->some_function();</code>
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]270
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]271
272<h3>Setting Your Own Prefix</h3>
273
274<p>To set your own sub-class prefix, open your <dfn>application/config/config.php</dfn> file and look for this item:</p>
275
276<code>$config['subclass_prefix'] = 'MY_';</code>
277
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]278<p>Please note that all native CodeIgniter libraries are prefixed with <kbd>CI_</kbd> so DO NOT use that as your prefix.</p>
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]279
280
281
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]282</div>
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287<p>
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]288Previous Topic:&nbsp;&nbsp;<a href="libraries.html">Using CodeIgniter Libraries</a>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]289&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
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admina634e562006-08-25 22:19:55 +0000[diff] [blame]292Next Topic:&nbsp;&nbsp;<a href="core_classes.html">Creating Core System Classes</a>
Derek Allardc6441282007-07-04 23:54:32 +0000[diff] [blame]293</p>
Derek Jones07870432008-02-13 03:49:26 +0000[diff] [blame]294<p><a href="http://codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2006-2008 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">Ellislab, Inc.</a></p>
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