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| <h1>Creating Libraries</h1> | |
| <p>When we use the term "Libraries" we are normally referring to the classes that are located in the <kbd>libraries</kbd> | |
| directory and described in the Class Reference of this user guide. In this case, however, we will instead describe how you can create | |
| your own libraries within your <dfn>application/libraries</dfn> directory in order to maintain separation between your local resources | |
| and the global framework resources.</p> | |
| <p>As an added bonus, CodeIgniter permits your libraries to <kbd>extend</kbd> native classes if you simply need to add some functionality | |
| to an existing library. Or you can even replace native libraries just by placing identically named versions in your <dfn>application/libraries</dfn> folder.</p> | |
| <p>In summary:</p> | |
| <ul> | |
| <li>You can create entirely new libraries.</li> | |
| <li>You can extend native libraries.</li> | |
| <li>You can replace native libraries.</li> | |
| </ul> | |
| <p>The page below explains these three concepts in detail.</p> | |
| <p class="important"><strong>Note:</strong> The Database classes can not be extended or replaced with your own classes, | |
| nor can the main Controller class. All other classes are able to be replaced/extended.</p> | |
| <h2>Storage</h2> | |
| <p>Your library classes should be placed within your <dfn>application/libraries</dfn> folder, as this is where CodeIgniter will look for them when | |
| they are initialized.</p> | |
| <h2>Naming Conventions</h2> | |
| <ul> | |
| <li>File names must be capitalized. For example: <dfn>Myclass.php</dfn></li> | |
| <li>Class declarations must be capitalized. For example: <kbd>class Myclass</kbd></li> | |
| <li>Class names and file names must match.</li> | |
| </ul> | |
| <h2>The Class File</h2> | |
| <p>Classes should have this basic prototype (Note: We are using the name <kbd>Someclass</kbd> purely as an example):</p> | |
| <code><?php if (!defined('BASEPATH')) exit('No direct script access allowed'); | |
| <br /><br /> | |
| class Someclass {<br /> | |
| <br /> | |
| function some_function()<br /> | |
| {<br /> | |
| }<br /> | |
| }<br /><br /> | |
| ?></code> | |
| <h2>Using Your Class</h2> | |
| <p>From within any of your <a href="controllers.html">Controller</a> functions you can initialize your class using the standard:</p> | |
| <code>$this->load->library('<kbd>someclass</kbd>');</code> | |
| <p>Where <em>someclass</em> is the file name, without the ".php" file extension. You can submit the file name capitalized or lower case. | |
| CodeIgniter doesn't care.</p> | |
| <p>Once loaded you can access your class using the <kbd>lower case</kbd> version:</p> | |
| <code>$this-><kbd>someclass</kbd>->some_function(); // Object instances will always be lower case | |
| </code> | |
| <h2>Passing Parameters When Initializing Your Class</h2> | |
| <p>In the library loading function you can dynamically pass data via the second parameter and it will be passed to your class | |
| constructor:</p> | |
| <code> | |
| $params = array('type' => 'large', 'color' => 'red');<br /> | |
| <br /> | |
| $this->load->library('Someclass', <kbd>$params</kbd>);</code> | |
| <p>If you use this feature you must set up your class constructor to expect data:</p> | |
| <code><?php if (!defined('BASEPATH')) exit('No direct script access allowed');<br /> | |
| <br /> | |
| class Someclass {<br /> | |
| <br /> | |
| function Someclass($params)<br /> | |
| {<br /> | |
| // Do something with $params<br /> | |
| }<br /> | |
| }<br /><br /> | |
| ?></code> | |
| <p class="important">You can also pass parameters stored in a config file. Simply create a config file named identically to the class <kbd>file name</kbd> | |
| and store it in your <dfn>application/config/</dfn> folder. Note that if you dynamically pass parameters as described above, | |
| the config file option will not be available.</p> | |
| <h2>Utilizing CodeIgniter Resources within Your Library</h2> | |
| <p>To access CodeIgniter's native resources within your library use the <kbd>get_instance()</kbd> function. | |
| This function returns the CodeIgniter super object.</p> | |
| <p>Normally from within your controller functions you will call any of the available CodeIgniter functions using the <kbd>$this</kbd> construct:</p> | |
| <code> | |
| <strong>$this</strong>->load->helper('url');<br /> | |
| <strong>$this</strong>->load->library('session');<br /> | |
| <strong>$this</strong>->config->item('base_url');<br /> | |
| etc. | |
| </code> | |
| <p><kbd>$this</kbd>, however, only works directly within your controllers, your models, or your views. | |
| If you would like to use CodeIgniter's classes from within your own custom classes you can do so as follows:</p> | |
| <p>First, assign the CodeIgniter object to a variable:</p> | |
| <code>$CI =& get_instance();</code> | |
| <p>Once you've assigned the object to a variable, you'll use that variable <em>instead</em> of <kbd>$this</kbd>:</p> | |
| <code> | |
| $CI =& get_instance();<br /><br /> | |
| $CI->load->helper('url');<br /> | |
| $CI->load->library('session');<br /> | |
| $CI->config->item('base_url');<br /> | |
| etc. | |
| </code> | |
| <p class="important"><strong>Note:</strong> You'll notice that the above get_instance() function is being passed by reference: | |
| <br /><br /> | |
| <var>$CI =& get_instance();</var> | |
| <br /><br /> | |
| <kbd>This is very important.</kbd> Assigning by reference allows you to use the original CodeIgniter object rather than creating a copy of it. | |
| <br /><br /> | |
| <kbd>Also, please note:</kbd> If you are running PHP 4 it's usually best to avoid calling <dfn>get_instance()</dfn> | |
| from within your class constructors. PHP 4 has trouble referencing the CI super object within application constructors | |
| since objects do not exist until the class is fully instantiated.</p> | |
| <h2>Replacing Native Libraries with Your Versions</h2> | |
| <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 | |
| feature 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 | |
| you'll create a file named <dfn>application/libraries/Email.php</dfn>, and declare your class with:</p> | |
| <code> | |
| class CI_Email {<br /><br /> | |
| }</code> | |
| <p>Note that most native classes are prefixed with <kbd>CI_</kbd>.</p> | |
| <p>To load your library you'll see the standard loading function:</p> | |
| <code>$this->load->library('<kbd>email</kbd>');</code> | |
| <p class="important"><strong>Note:</strong> At this time the Database classes can not be replaced with your own versions.</p> | |
| <h2>Extending Native Libraries</h2> | |
| <p>If all you need to do is add some functionality to an existing library - perhaps add a function or two - then | |
| it's overkill to replace the entire library with your version. In this case it's better to simply extend the class. | |
| Extending a class is nearly identical to replacing a class with a couple exceptions:</p> | |
| <ul> | |
| <li>The class declaration must extend the parent class.</li> | |
| <li>Your new class name and filename must be prefixed with <kbd>MY_</kbd> (this item is configurable. See below.).</li> | |
| </ul> | |
| <p>For example, to extend the native <kbd>Email</kbd> class you'll create a file named <dfn>application/libraries/</dfn><kbd>MY_Email.php</kbd>, and declare your class with:</p> | |
| <code> | |
| class MY_Email extends CI_Email {<br /><br /> | |
| }</code> | |
| <p>Note: If you need to use a constructor in your class make sure you extend the parent constructor:</p> | |
| <code> | |
| class MY_Email extends CI_Email {<br /> | |
| <br /> | |
| function My_Email()<br /> | |
| {<br /> | |
| parent::CI_Email();<br /> | |
| }<br /> | |
| }</code> | |
| <h3>Loading Your Sub-class</h3> | |
| <p>To load your sub-class you'll use the standard syntax normally used. DO NOT include your prefix. For example, | |
| to load the example above, which extends the Email class, you will use:</p> | |
| <code>$this->load->library('<kbd>email</kbd>');</code> | |
| <p>Once loaded you will use the class variable as you normally would for the class you are extending. In the case of | |
| the email class all calls will use:</p> | |
| <code>$this-><kbd>email</kbd>->some_function();</code> | |
| <h3>Setting Your Own Prefix</h3> | |
| <p>To set your own sub-class prefix, open your <dfn>application/config/config.php</dfn> file and look for this item:</p> | |
| <code>$config['subclass_prefix'] = 'MY_';</code> | |
| <p>Please note that all native CodeIgniter libraries are prefixed with <kbd>CI_</kbd> so DO NOT use that as your prefix.</p> | |
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