__invoke() magic method

__invoke() magic method might seem similar like __construct() magic method but there's a vital difference here. Which we'll look into using few examples.

What __invoke() magic method basically does is it makes a class callable.

First Example

class DevClass 
{
	public function __invoke(){
		var_dump('invoked');
	}
}

$dev = new DevClass();

var_dump(is_callable($dev));

Here, we’ve a simple DevClass with __invoke() magic method. Notice that upon initializing the class, it does nothing as it does in case of __construct() magic method. If we call is_callable() on DevClass object we’ll get true. But in case we comment out the __invoke() magic method, we get false. In short __invoke() magic magic makes a class callable.

Now you must be thinking, why’d we want to make a class callable & what’s the purpose of doing it. We’ll look this in the next example.

Second Example (Class as a function)

class HomeController
{
	public function index(){
		var_dump("hello from devpeel");
	}
}

$controller = new HomeController();
$controller->index();

This is a usual example of some index method inside of a class and the simple way of calling it. But we’ve scenarios where we’re registering our Controllers or classes, we don’t always want to give method name & what we can rather do is actually use the __invoke() magic method & our class will anonymously run exactly the same but acts as a method instead & the _invoke() magic method will handle the rendering. This kind of approach you shall see in frameworks like Laravel as well. See the code below for reference.

class HomeController
{
	public function __invoke(){
		var_dump("hello from devpeel");
	}
}

$controller = new HomeController();
$controller();

Another Example

Now look at another practical example where __invoke() magic method can be used to tidy things up a little. Below is the simple class AddNumbers which adds two numbers,

class AddNumbers
{
	protected $to;
	protected $value;
	public function __construct($to, $value)
	{
		$this->to = $to;
		$this->value = $value;
	}

	public function result(){
		return $this->to + $this->value;
	}

}

$add = new AddNumbers(10,10);

var_dump($add->result());

Now let’s clean this up a bit. We’ll add the __invoke() magic method here to tidy things up and improve our API for the class.

class AddNumbers
{
	protected $to;
	protected $value;
	public function __construct($to, $value)
	{
		$this->to = $to;
		$this->value = $value;
	}

	public function __invoke(){
		return $this->result();
	}

	public function result(){
		return $this->to + $this->value;
	}

}

$add = new AddNumbers(10,10);

var_dump($add());

Now as you can see, we can now call the class as method, moreover we can move the result() method functionality to __invoke() magic method to further clean up the code as well.

Another Example (Passing values)

If you’re wondering as if we can pass values inside of __invoke() magic method, yes we can. Let’s have a look.

class DevClass
{
	
	public function __invoke($value){
		var_dump($value);
	}

}

$class = new DevClass();

$class('PHP is Awesome');