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<td><h1>CodeIgniter User Guide Version 2.1.3</h1></td>
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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>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>application/helpers </dfn>directory. CodeIgniter will look first in your <dfn>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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// 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, $haystack)<br />
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$needle = (is_array($needle)) ? $needle : array($needle);<br />
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foreach ($needle as $item)<br />
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{<br />
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if (in_array($item, $haystack))<br />
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{<br />
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return TRUE;<br />
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}<br />
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}<br />
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return FALSE;<br />
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// random_element() is included in Array Helper, so it overrides the native function<br />
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function random_element($array)<br />
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shuffle($array);<br />
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return array_pop($array);<br />
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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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<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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