################
Helper Functions
################

Helpers, as the name suggests, help you with tasks. Each helper file is
simply a collection of functions in a particular category. There are **URL
Helpers**, that assist in creating links, there are **Form Helpers** that help
you create form elements, **Text Helpers** perform various text formatting
routines, **Cookie Helpers** set and read cookies, **File Helpers** help you
deal with files, etc.

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.

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 :doc:`controller <../general/controllers>` and
:doc:`views <../general/views>`.

Helpers are typically stored in your **system/Helpers**, or
**application/Helpers directory**. CodeIgniter will look first in your
**application/Helpers directory**. If the directory does not exist or the
specified helper is not located there CI will instead look in your
global *system/Helpers/* directory.

Loading a Helper
================

Loading a helper file is quite simple using the following method::

	helper('name');

Where **name** is the file name of the helper, without the .php file
extension or the "helper" part.

For example, to load the **Cookie Helper** file, which is named
**cookie_helper.php**, you would do this::

	helper('cookie');

If you need to load more than one helper at a time, you can pass
an array of file names in and all of them will be loaded::

	helper(['cookie', 'date']);

A helper can be loaded anywhere within your controller methods (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.

.. note:: The Helper loading method above does not return a value, so
	don't try to assign it to a variable. Just use it as shown.

.. note:: The URL helper is always loaded so you do not need to load it yourself.

Loading from Non-standard Locations
-----------------------------------

Helpers can be loaded from directories outside of **application/Helpers** and
**system/Helpers**, as long as that path can be found through a namespace that
has been setup within the PSR-4 section of the :doc:`Autoloader config file <../concepts/autoloader>`.
You would prefix the name of the Helper with the namespace that it can be located
in. Within that namespaced directory, the loader expects it to live within a
sub-directory named ``Helpers``. An example will help understand this.

For this example, assume that we have grouped together all of our Blog-related
code into its own namespace, ``Example\Blog``. The files exist on our server at
**/Modules/Blog/**. So, we would put our Helper files for the blog module in
**/Modules/Blog/Helpers/**. A **blog_helper** file would be at
**/Modules/Blog/Helpers/blog_helper.php**. Within our controller we could
use the following command to load the helper for us::

	helper('Modules\Blog\blog');

.. note:: The functions within files loaded this way are not truly namespaced.
		The namespace is simply used as a convenient way to locate the files.

Using a Helper
==============

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.

For example, to create a link using the ``anchor()`` function in one of
your view files you would do this::

	<?php echo anchor('blog/comments', 'Click Here');?>

Where "Click Here" is the name of the link, and "blog/comments" is the
URI to the controller/method you wish to link to.

"Extending" Helpers
===================

TODO: Determine how these can be extended... namespaces, etc?

To "extend" Helpers, create a file in your **application/helpers/** folder
with an identical name to the existing Helper, but prefixed with **MY\_**
(this item is configurable. See below.).

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.

.. note:: 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 or or to replace the functions a Helper provides.

For example, to extend the native **Array Helper** you'll create a file
named **application/helpers/MY_array_helper.php**, and add or override
functions::

	// any_in_array() is not in the Array Helper, so it defines a new function
	function any_in_array($needle, $haystack)
	{
		$needle = is_array($needle) ? $needle : array($needle);

		foreach ($needle as $item)
		{
			if (in_array($item, $haystack))
			{
				return TRUE;
			}
	        }

		return FALSE;
	}

	// random_element() is included in Array Helper, so it overrides the native function
	function random_element($array)
	{
		shuffle($array);
		return array_pop($array);
	}

Now What?
=========

In the Table of Contents you'll find a list of all the available Helper
Files. Browse each one to see what they do.
