Import and export only a function under namespace in PHP
The standard way of including files in modern PHP development is using namespaces and autoloading of classes using Composer.
So, for instance, if I have the autoload setup like following in my composer.json…
{
...
"autoload": {
"psr-4": {
"App\\": "app/"
}
}
...
}
…And I have a file called HelloWorld.php under app/ which contains a HelloWorld class, we can define it using namespace like so.
<?php
namespace App;
class HelloWorld
{
}
You can use/import this class in other files like so.
use App\HelloWorld;
A function under a namespace
Recently, I was going through all the new features of Laravel 8 and I saw this queueable function which can be used to mark the closure based listeners as “queueable”. And this is the first time where I’ve seen only a function being defined under a namespace.
If we look closely at the source code of it, we get to know that the queueable function lies under the Illuminate\Events namespace like so.
//src/Illuminate/Events/functions.php
<?php
namespace Illuminate\Events;
use Closure;
if (! function_exists('Illuminate\Events\queueable')) {
/**
* Create a new queued Closure event listener.
*
* @param \Closure $closure
* @return \Illuminate\Events\QueuedClosure
*/
function queueable(Closure $closure)
{
return new QueuedClosure($closure);
}
}
As you can tell, the src/Illuminate/Events/functions.php only contains a function queueable under the namespace Illuminate\Events.
And because it’s under a namespace, you can import it elsewhere using the use function operator like so and start using it just like that.
use function Illuminate\Events\queueable;
Usefulness
This is especially useful, in my opinion, in scenarios where you don’t want to create an entire class for a single function but still want to keep it under a namespace so that it’s easily importable like in the case of this queueable function.
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