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 controller and views.
Helpers are typically stored in your system/Helpers, or app/Helpers directory. CodeIgniter will look first in your app/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 app/Helpers and system/Helpers, as long as that path can be found through a namespace that has been set up within the PSR-4 section of the Autoloader config file. 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('Example\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:
<?= 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
To “extend” Helpers, create a file in your app/Helpers/ folder with an identical name to the existing Helper.
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 to replace the functions a Helper provides.
For example, to extend the native Array Helper you’ll create a file named app/Helpers/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) ? $needle : [$needle];
foreach ($needle as $item) {
if (in_array($item, $haystack, true)) {
return true;
}
}
return false;
}
// random_element() is included in Array Helper, so it overrides the native function
function random_element($array)
{
shuffle($array);
return array_pop($array);
}
The helper() method will scan through all PSR-4 namespaces defined in app/Config/Autoload.php
and load in ALL matching helpers of the same name. This allows any module’s helpers
to be loaded, as well as any helpers you’ve created specifically for this application. The load order
is as follows:
app/Helpers - Files loaded here are always loaded first.
{namespace}/Helpers - All namespaces are looped through in the order they are defined.
system/Helpers - The base file is loaded last