185 lines
8.8 KiB
HTML
185 lines
8.8 KiB
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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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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>Helper Functions : CodeIgniter User Guide</title>
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<style type='text/css' media='all'>@import url('../userguide.css');</style>
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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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<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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<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 1.7.3</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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<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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Helper Functions
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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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</table>
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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>Helper Functions</h1>
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<p>Helpers, as the name suggests, help you with tasks. Each helper file is simply a collection of functions in a particular
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category. There are <dfn>URL Helpers</dfn>, that assist in creating links, there are <dfn>Form Helpers</dfn>
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that help you create form elements, <dfn>Text Helpers</dfn> perform various text formatting routines,
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<dfn>Cookie Helpers</dfn> set and read cookies, <dfn>File Helpers</dfn> help you deal with files, etc.
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</p>
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<p>Unlike most other systems in CodeIgniter, Helpers are not written in an Object Oriented format. They are simple, procedural functions.
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Each helper function performs one specific task, with no dependence on other functions.</p>
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<p>CodeIgniter does not load Helper Files by default, so the first step in using
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a Helper is to load it. Once loaded, it becomes globally available in your <a href="../general/controllers.html">controller</a> and <a href="../general/views.html">views</a>.</p>
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<p>Helpers are typically stored in your <dfn>system/helpers</dfn>, or <dfn>system/application/helpers </dfn>directory. CodeIgniter will look first in your <dfn>system/application/helpers</dfn>
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directory. If the directory does not exist or the specified helper is not located there CI will instead look in your global
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<dfn>system/helpers</dfn> folder.</p>
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<h2>Loading a Helper</h2>
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<p>Loading a helper file is quite simple using the following function:</p>
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<code>$this->load->helper('<var>name</var>');</code>
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<p>Where <var>name</var> is the file name of the helper, without the .php file extension or the "helper" part.</p>
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<p>For example, to load the <dfn>URL Helper</dfn> file, which is named <var>url_helper.php</var>, you would do this:</p>
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<code>$this->load->helper('<var>url</var>');</code>
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<p>A helper can be loaded anywhere within your controller functions (or even within your View files, although that's not a good practice),
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as long as you load it before you use it. You can load your helpers in your controller constructor so that they become available
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automatically in any function, or you can load a helper in a specific function that needs it.</p>
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<p class="important">Note: The Helper loading function above does not return a value, so don't try to assign it to a variable. Just use it as shown.</p>
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<h2>Loading Multiple Helpers</h2>
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<p>If you need to load more than one helper you can specify them in an array, like this:</p>
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<code>$this->load->helper( <samp>array(</samp>'<var>helper1</var>', '<var>helper2</var>', '<var>helper3</var>'<samp>)</samp> );</code>
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<h2>Auto-loading Helpers</h2>
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<p>If you find that you need a particular helper globally throughout your application, you can tell CodeIgniter to auto-load it during system initialization.
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This is done by opening the <var>application/config/autoload.php</var> file and adding the helper to the autoload array.</p>
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<h2>Using a Helper</h2>
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<p>Once you've loaded the Helper File containing the function you intend to use, you'll call it the way you would a standard PHP function.</p>
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<p>For example, to create a link using the <dfn>anchor()</dfn> function in one of your view files you would do this:</p>
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<code><?php echo anchor('blog/comments', 'Click Here');?></code>
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<p>Where "Click Here" is the name of the link, and "blog/comments" is the URI to the controller/function you wish to link to.</p>
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<h2>"Extending" Helpers</h2>
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<p>To "extend" Helpers, create a file in your <dfn>application/helpers/</dfn> folder with an identical name to the existing Helper, but prefixed with <kbd>MY_</kbd> (this item is configurable. See below.).</p>
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<p>If all you need to do is add some functionality to an existing helper - perhaps add a function or two, or change how a particular
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helper function operates - then it's overkill to replace the entire helper with your version. In this case it's better to simply
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"extend" the Helper. The term "extend" is used loosely since Helper functions are procedural and discrete and cannot be extended
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in the traditional programmatic sense. Under the hood, this gives you the ability to add to the functions a Helper provides,
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or to modify how the native Helper functions operate.</p>
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<p>For example, to extend the native <kbd>Array Helper</kbd> you'll create a file named <dfn>application/helpers/</dfn><kbd>MY_array_helper.php</kbd>, and add or override functions:</p>
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<code>
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// any_in_array() is not in the Array Helper, so it defines a new function<br />
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function any_in_array($needle, $haystack)<br />
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{<br />
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$needle = (is_array($needle)) ? $needle : array($needle);<br />
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<br />
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foreach ($needle as $item)<br />
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{<br />
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if (in_array($item, $haystack))<br />
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{<br />
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return TRUE;<br />
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}<br />
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}<br />
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<br />
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return FALSE;<br />
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}<br />
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<br />
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// random_element() is included in Array Helper, so it overrides the native function<br />
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function random_element($array)<br />
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{<br />
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shuffle($array);<br />
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return array_pop($array);<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>The filename prefix for "extending" Helpers is the same used to extend libraries and Core classes. To set your own 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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<h2>Now What?</h2>
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<p>In the Table of Contents you'll find a list of all the available Helper Files. Browse each one to see what they do.</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="models.html">Models</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="plugins.html">Plugins</a>
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</p>
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<p><a href="http://codeigniter.com">CodeIgniter</a> · Copyright © 2006-2010 · <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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