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50Creating Libraries
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61<div id="content">
62
63<h1>Creating Libraries</h1>
64
65<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]66directory and described in the Class Reference of this user guide. In this case, however, we will instead describe how you can create
67your 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]68and the global framework resources.</p>
69
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]70<p>As an added bonus, CodeIgniter permits your libraries to <kbd>extend</kbd> native classes if you simply need to add some functionality
admin33de9a12006-09-28 06:50:16 +0000[diff] [blame]71to an existing library. Or you can even replace native libraries just by placing identically named versions in your <dfn>application/libraries</dfn> folder.
72
73<p>In summary:</p>
74
75<ul>
76<li>You can create entirely new libraries.</li>
77<li>You can extend native libraries.</li>
78<li>You can replace native libraries.</li>
79</ul>
80
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]81<p>The page below explains these three concepts in detail.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]82
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]83<p class="important"><strong>Note:</strong> The Database classes can not be extended or replaced with your own classes,
84nor can the main Controller class. All other classes are able to be replaced/extended.</p>
85
86
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]87<h2>Storage</h2>
88
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]89<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]90they are initialized.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]91
92
93<h2>Naming Conventions</h2>
94
95<ul>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]96<li>File names must be capitalized. For example:&nbsp; <dfn>Myclass.php</dfn></li>
97<li>Class declarations must be capitalized. For example:&nbsp; <kbd>class Myclass</kbd></li>
98<li>Class names and file names must match.</li>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]99</ul>
100
101
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]102<h2>The Class File</h2>
103
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]104<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]105
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]106<code>&lt;?php if (!defined('BASEPATH')) exit('No direct script access allowed');
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]107<br /><br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]108class Someclass {<br />
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]109<br />
110&nbsp;&nbsp;&nbsp;&nbsp;function some_function()<br />
111&nbsp;&nbsp;&nbsp;&nbsp;{<br />
112&nbsp;&nbsp;&nbsp;&nbsp;}<br />
113}<br /><br />
114?&gt;</code>
115
116
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]117<h2>Using Your Class</h2>
118
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]119<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]120
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]121<code>$this->load->library('<kbd>someclass</kbd>');</code>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]122
admine334c472006-10-21 19:44:22 +0000[diff] [blame]123<p>Where <em>someclass</em> is the file name, without the ".php" file extension. You can submit the file name capitalized or lower case.
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]124CodeIgniter doesn't care.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]125
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]126<p>Once loaded you can access your class using the <kbd>lower case</kbd> version:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]127
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]128<code>$this-><kbd>someclass</kbd>->some_function();&nbsp; // Object instances will always be lower case
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]129</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]130
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]131
132
133<h2>Passing Parameters When Initializing Your Class</h2>
134
admine334c472006-10-21 19:44:22 +0000[diff] [blame]135<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]136constructor:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]137
138<code>
139$params = array('type' => 'large', 'color' => 'red');<br />
140<br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]141$this->load->library('Someclass', <kbd>$params</kbd>);</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]142
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]143<p>If you use this feature you must set up your class constructor to expect data:</p>
144
145<code>&lt;?php if (!defined('BASEPATH')) exit('No direct script access allowed');<br />
146<br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]147class Someclass {<br />
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]148<br />
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]149&nbsp;&nbsp;&nbsp;&nbsp;function Someclass($params)<br />
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]150&nbsp;&nbsp;&nbsp;&nbsp;{<br />
151&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Do something with $params<br />
152&nbsp;&nbsp;&nbsp;&nbsp;}<br />
153}<br /><br />
154?&gt;</code>
155
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]156<p class="important">You can also pass parameters stored in a config file. Simply create a config file named identically to the class <kbd>file name</kbd>
157and store it in your <dfn>application/config/</dfn> folder. Note that if you dynamically pass parameters as described above,
158the config file option will not be available.</p>
adminebbe3832006-09-26 06:02:47 +0000[diff] [blame]159
160
161
162
163
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]164
165
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]166<h2>Utilizing CodeIgniter Resources within Your Library</h2>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]167
168
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]169<p>To access CodeIgniter's native resources within your library use the <kbd>get_instance()</kbd> function.
170This function returns the CodeIgniter super object.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]171
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]172<p>Normally from within your controller functions you will call any of the available CodeIgniter functions using the <kbd>$this</kbd> construct:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]173
174<code>
175<strong>$this</strong>->load->helper('url');<br />
176<strong>$this</strong>->load->library('session');<br />
177<strong>$this</strong>->config->item('base_url');<br />
178etc.
179</code>
180
admine334c472006-10-21 19:44:22 +0000[diff] [blame]181<p><kbd>$this</kbd>, however, only works directly within your controllers, your models, or your views.
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]182If 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]183
184
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]185<p>First, assign the CodeIgniter object to a variable:</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]186
admin88a8ad12006-10-07 03:16:32 +0000[diff] [blame]187<code>$CI =& get_instance();</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]188
189<p>Once you've assigned the object to a variable, you'll use that variable <em>instead</em> of <kbd>$this</kbd>:</p>
190
191<code>
admin88a8ad12006-10-07 03:16:32 +0000[diff] [blame]192$CI =& get_instance();<br /><br />
193$CI->load->helper('url');<br />
194$CI->load->library('session');<br />
195$CI->config->item('base_url');<br />
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]196etc.
197</code>
198
199<p class="important"><strong>Note:</strong> You'll notice that the above get_instance() function is being passed by reference:
200<br /><br />
admin88a8ad12006-10-07 03:16:32 +0000[diff] [blame]201<var>$CI =& get_instance();</var>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]202<br /><br />
Rick Ellis1f852632007-06-09 00:25:57 +0000[diff] [blame]203<kbd>This is very important.</kbd> Assigning by reference allows you to use the original CodeIgniter object rather than creating a copy of it.
204<br /><br />
205<kbd>Also, please note:</kbd> If you are running PHP 4 it's usually best to avoid calling <dfn>get_instance()</dfn>
206from within your class constructors. PHP 4 has trouble referencing the CI super object within application constructors
207since objects do not exist until the class is fully instantiated.</p>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]208
209
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]210<h2>Replacing Native Libraries with Your Versions</h2>
211
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]212<p>Simply by naming your class files identically to a native library will cause CodeIgniter to use it instead of the native one. To use this
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]213feature you must name the file and the class declaration exactly the same as the native library. For example, to replace the native <kbd>Email</kbd> library
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]214you'll create a file named <dfn>application/libraries/Email.php</dfn>, and declare your class with:</p>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]215
216<code>
217class CI_Email {<br /><br />
218
219}</code>
220
221<p>Note that most native classes are prefixed with <kbd>CI_</kbd>.</p>
222
223<p>To load your library you'll see the standard loading function:</p>
224
225<code>$this->load->library('<kbd>email</kbd>');</code>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]226
Derek Allard7a1f5162007-01-27 18:02:09 +0000[diff] [blame]227<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]228
229
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]230<h2>Extending Native Libraries</h2>
231
232<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]233it's overkill to replace the entire library with your version. In this case it's better to simply extend the class.
234Extending a class is nearly identical to replacing a class with a couple exceptions:</p>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]235
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]236<ul>
237<li>The class declaration must extend the parent class.</li>
admine334c472006-10-21 19:44:22 +0000[diff] [blame]238<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]239</ul>
240
241<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]242
243<code>
244class MY_Email extends CI_Email {<br /><br />
245
246}</code>
247
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]248<p>Note: If you need to use a constructor in your class make sure you extend the parent constructor:</p>
249
250
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]251<code>
252class MY_Email extends CI_Email {<br />
253<br />
254&nbsp;&nbsp;&nbsp;&nbsp;function My_Email()<br />
255&nbsp;&nbsp;&nbsp;&nbsp;{<br />
256&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;parent::CI_Email();<br />
257&nbsp;&nbsp;&nbsp;&nbsp;}<br />
258}</code>
259
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]260
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]261<h3>Loading Your Sub-class</h3>
262
263<p>To load your sub-class you'll use the standard syntax normally used. DO NOT include your prefix. For example,
264to load the example above, which extends the Email class, you will use:</p>
265
266<code>$this->load->library('<kbd>email</kbd>');</code>
admine1bf9422006-09-28 07:15:05 +0000[diff] [blame]267
admine334c472006-10-21 19:44:22 +0000[diff] [blame]268<p>Once loaded you will use the class variable as you normally would for the class you are extending. In the case of
admincf493902006-10-10 07:12:31 +0000[diff] [blame]269the email class all calls will use:
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]270
271
admincf493902006-10-10 07:12:31 +0000[diff] [blame]272<code>$this-><kbd>email</kbd>->some_function();</code>
admin79c643d2006-09-28 07:26:21 +0000[diff] [blame]273
admin0625e192006-10-20 22:16:54 +0000[diff] [blame]274
275<h3>Setting Your Own Prefix</h3>
276
277<p>To set your own sub-class prefix, open your <dfn>application/config/config.php</dfn> file and look for this item:</p>
278
279<code>$config['subclass_prefix'] = 'MY_';</code>
280
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]281<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]282
283
284
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290<p>
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]291Previous Topic:&nbsp;&nbsp;<a href="libraries.html">Using CodeIgniter Libraries</a>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]292&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
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admina634e562006-08-25 22:19:55 +0000[diff] [blame]295Next Topic:&nbsp;&nbsp;<a href="core_classes.html">Creating Core System Classes</a>
adminb0dd10f2006-08-25 17:25:49 +0000[diff] [blame]296<p>
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]297<p><a href="http://www.codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2007 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">Ellislab, Inc.</a></p>
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