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+<td><h1>CodeIgniter User Guide Version 2.0.2</h1></td>
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+Creating Libraries
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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. 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 />
+ public function some_function()<br />
+ {<br />
+ }<br />
+}<br /><br />
+/* End of file Someclass.php */</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 as an array 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>$params</kbd>);</code>
+
+<p>If you use this feature you must set up your class constructor to expect data:</p>
+
+<code><?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');<br />
+<br />
+class Someclass {<br />
+<br />
+ public function __construct($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>$CI =& get_instance();</var>
+<br />
+<br />
+<kbd>This is very important.</kbd> Assigning by reference allows you to use the original CodeIgniter object rather than creating a copy of it.</p>
+
+
+<h2>Replacing Native Libraries with Your Versions</h2>
+
+<p>Simply by naming your class files identically to a native library will cause CodeIgniter to use it instead of the native one. To use this
+feature you must name the file and the class declaration exactly the same as the native library. For example, to replace the native <kbd>Email</kbd> library
+you'll create a file named <dfn>application/libraries/Email.php</dfn>, and declare your class with:</p>
+
+<code>
+class CI_Email {<br /><br />
+
+}</code>
+
+<p>Note that most native classes are prefixed with <kbd>CI_</kbd>.</p>
+
+<p>To load your library you'll see the standard loading function:</p>
+
+<code>$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 />
+ public function __construct()<br />
+ {<br />
+ parent::__construct();<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>
+
+
+
+</div>
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