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| <h1>Helper Functions</h1> | |
| <p>Helpers, as the name suggests, help you with tasks. Each helper file is simply a collection of functions in a particular | |
| category. There are <dfn>URL Helpers</dfn>, that assist in creating links, there are <dfn>Form Helpers</dfn> | |
| that help you create form elements, <dfn>Text Helpers</dfn> perform various text formatting routines, | |
| <dfn>Cookie Helpers</dfn> set and read cookies, <dfn>File Helpers</dfn> help you deal with files, etc. | |
| </p> | |
| <p>Unlike most other systems in CodeIgniter, Helpers are not written in an Object Oriented format. They are simple, procedural functions. | |
| Each helper function performs one specific task, with no dependence on other functions.</p> | |
| <p>CodeIgniter does not load Helper Files by default, so the first step in using | |
| 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> | |
| <p>Helpers are typically stored in your <dfn>system/helpers</dfn> directory. Alternately you can create a folder called <kbd>helpers</kbd> inside | |
| your <kbd>application</kbd> folder and store them there. CodeIgniter will look first in your <dfn>system/application/helpers</dfn> | |
| directory. If the directory does not exist or the specified helper is not located there CI will instead look in your global | |
| <dfn>system/helpers</dfn> folder.</p> | |
| <h2>Loading a Helper</h2> | |
| <p>Loading a helper file is quite simple using the following function:</p> | |
| <code>$this->load->helper('<var>name</var>');</code> | |
| <p>Where <var>name</var> is the file name of the helper, without the .php file extension or the "helper" part.</p> | |
| <p>For example, to load the <dfn>URL Helper</dfn> file, which is named <var>url_helper.php</var>, you would do this:</p> | |
| <code>$this->load->helper('<var>url</var>');</code> | |
| <p>A helper can be loaded anywhere within your controller functions (or even within your View files, although that's not a good practice), | |
| as long as you load it before you use it. You can load your helpers in your controller constructor so that they become available | |
| automatically in any function, or you can load a helper in a specific function that needs it.</p> | |
| <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> | |
| <h2>Loading Multiple Helpers</h2> | |
| <p>If you need to load more than one helper you can specify them in an array, like this:</p> | |
| <code>$this->load->helper( <samp>array(</samp>'<var>helper1</var>', '<var>helper2</var>', '<var>helper3</var>'<samp>)</samp> );</code> | |
| <h2>Auto-loading Helpers</h2> | |
| <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. | |
| This is done by opening the <var>application/config/autoload.php</var> file and adding the helper to the autoload array.</p> | |
| <h2>Using a Helper</h2> | |
| <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> | |
| <p>For example, to create a link using the <dfn>anchor()</dfn> function in one of your view files you would do this:</p> | |
| <code><?=anchor('blog/comments', 'Click Here');?></code> | |
| <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> | |
| <h2>"Extending" Helpers</h2> | |
| <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> | |
| <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 | |
| helper function operates - then it's overkill to replace the entire helper with your version. In this case it's better to simply | |
| "extend" the Helper. The term "extend" is used loosely since Helper functions are procedural and discrete and cannot be extended | |
| in the traditional programmatic sense. Under the hood, this gives you the ability to add to the functions a Helper provides, | |
| or to modify how the native Helper functions operate.</p> | |
| <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> | |
| <code> | |
| // any_in_array() is not in the Array Helper, so it defines a new function<br /> | |
| function any_in_array($needle, $haystack)<br /> | |
| {<br /> | |
| $needle = (is_array($needle)) ? $needle : array($needle);<br /> | |
| <br /> | |
| foreach ($needle as $item)<br /> | |
| {<br /> | |
| if (in_array($item, $haystack))<br /> | |
| {<br /> | |
| return TRUE;<br /> | |
| }<br /> | |
| }<br /> | |
| <br /> | |
| return FALSE;<br /> | |
| }<br /> | |
| <br /> | |
| // random_element() is included in Array Helper, so it overrides the native function<br /> | |
| function random_element($array)<br /> | |
| {<br /> | |
| shuffle($array);<br /> | |
| return array_pop();<br /> | |
| }<br /> | |
| </code> | |
| <h3>Setting Your Own Prefix</h3> | |
| <p>The filename prefix for "extending" Helpers is the same used to extend libraries and Core classes. To set your own prefix, open your <dfn>application/config/config.php</dfn> file and look for this item:</p> | |
| <code>$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> | |
| <h2>Now What?</h2> | |
| <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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