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186 lines
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>Creating Core System Classes : CodeIgniter User Guide</title>
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<style type='text/css' media='all'>@import url('../userguide.css');</style>
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<link rel='stylesheet' type='text/css' media='all' href='../userguide.css' />
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<script type="text/javascript" src="../nav/nav.js"></script>
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<meta http-equiv= 'pragma' content='no-cache' />
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<meta name='robots' content='all' />
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<meta name='author' content='ExpressionEngine Dev Team' />
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<meta name='description' content='CodeIgniter User Guide' />
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</head>
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<body>
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<!-- START NAVIGATION -->
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<div id="nav"><div id="nav_inner"><script type="text/javascript">create_menu('../');</script></div></div>
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<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="../images/nav_toggle_darker.jpg" width="154" height="43" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
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<div id="masthead">
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<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
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<tr>
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<td><h1>CodeIgniter User Guide Version 2.1.3</h1></td>
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<td id="breadcrumb_right"><a href="../toc.html">Table of Contents Page</a></td>
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</tr>
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</table>
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</div>
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<!-- END NAVIGATION -->
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<!-- START BREADCRUMB -->
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<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
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<tr>
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<td id="breadcrumb">
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<a href="http://codeigniter.com/">CodeIgniter Home</a> ›
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<a href="../index.html">User Guide Home</a> ›
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Creating Core System Classes
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</td>
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<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 <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" /> <input type="submit" class="submit" name="sa" value="Go" /></form></td>
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</tr>
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</table>
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<!-- END BREADCRUMB -->
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<br clear="all" />
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<!-- START CONTENT -->
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<div id="content">
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<h1>Creating Core System Classes</h1>
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<p>Every time CodeIgniter runs there are several base classes that are initialized automatically as part of the core framework.
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It is possible, however, to swap any of the core system classes with your own versions or even extend the core versions.</p>
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<p><strong>Most users will never have any need to do this,
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but the option to replace or extend them does exist for those who would like to significantly alter the CodeIgniter core.</strong>
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</p>
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<p class="important"><strong>Note:</strong> Messing with a core system class has a lot of implications, so make sure you
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know what you are doing before attempting it.</p>
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<h2>System Class List</h2>
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<p>The following is a list of the core system files that are invoked every time CodeIgniter runs:</p>
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<ul>
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<li>Benchmark</li>
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<li>Config</li>
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<li>Controller</li>
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<li>Exceptions</li>
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<li>Hooks</li>
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<li>Input</li>
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<li>Language</li>
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<li>Loader</li>
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<li>Log</li>
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<li>Output</li>
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<li>Router</li>
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<li>URI</li>
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<li>Utf8</li>
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</ul>
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<h2>Replacing Core Classes</h2>
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<p>To use one of your own system classes instead of a default one simply place your version inside your local <dfn>application/core</dfn> directory:</p>
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<code>application/core/<dfn>some-class.php</dfn></code>
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<p>If this directory does not exist you can create it.</p>
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<p>Any file named identically to one from the list above will be used instead of the one normally used.</p>
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<p>Please note that your class must use <kbd>CI</kbd> as a prefix. For example, if your file is named <kbd>Input.php</kbd> the class will be named:</p>
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<code>
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class CI_Input {<br /><br />
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}
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</code>
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<h2>Extending Core Class</h2>
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<p>If all you need to do is add some functionality to an existing library - perhaps add a function or two - then
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it's overkill to replace the entire library with your version. In this case it's better to simply extend the class.
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Extending a class is nearly identical to replacing a class with a couple exceptions:</p>
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<ul>
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<li>The class declaration must extend the parent class.</li>
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<li>Your new class name and filename must be prefixed with <kbd>MY_</kbd> (this item is configurable. See below.).</li>
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</ul>
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<p>For example, to extend the native <kbd>Input</kbd> class you'll create a file named <dfn>application/core/</dfn><kbd>MY_Input.php</kbd>, and declare your class with:</p>
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<code>
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class MY_Input extends CI_Input {<br /><br />
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}</code>
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<p>Note: If you need to use a constructor in your class make sure you extend the parent constructor:</p>
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<code>
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class MY_Input extends CI_Input {<br />
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<br />
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function __construct()<br />
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{<br />
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parent::__construct();<br />
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}<br />
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}</code>
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<p class="important"><strong>Tip:</strong> Any functions in your class that are named identically to the functions in the parent class will be used instead of the native ones
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(this is known as "method overriding").
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This allows you to substantially alter the CodeIgniter core.</p>
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<p>If you are extending the Controller core class, then be sure to extend your new class in your application controller's constructors.</p>
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<code>class Welcome extends MY_Controller {<br />
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<br />
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function __construct()<br />
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{<br />
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parent::__construct();<br />
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}<br />
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<br />
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function index()<br />
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{<br />
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$this->load->view('welcome_message');<br />
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}<br />
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}</code>
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<h3>Setting Your Own Prefix</h3>
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<p>To set your own sub-class prefix, open your <dfn>application/config/config.php</dfn> file and look for this item:</p>
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<code>$config['subclass_prefix'] = 'MY_';</code>
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<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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</div>
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<!-- END CONTENT -->
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<div id="footer">
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<p>
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Previous Topic: <a href="creating_libraries.html">Creating Your Own Libraries</a>
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·
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<a href="#top">Top of Page</a> ·
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<a href="../index.html">User Guide Home</a> ·
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Next Topic: <a href="hooks.html">Hooks - Extending the Core</a>
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</p>
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<p><a href="http://codeigniter.com">CodeIgniter</a> · Copyright © 2006 - 2012 · <a href="http://ellislab.com/">EllisLab, Inc.</a></p>
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</div>
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</body>
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</html>
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