php call nested function

Question

i wonder how php can achieve like below function design:

Class->func()->func()

Here is the laravel validate example.

    $validator->after(function($validator) 
    {
        if ($this->somethingElseIsInvalid()) 
        {
            **$validator->errors()->add('field', 'Something is wrong with this field!');**
        }
    });

Is the after() do the magic work here?

And how to create my own code that can behave like this.

Answer 1

Its called Method Chaining.

Method chaining works because a function or a method of the class always returns object which further call another function.

Basically it returns it self.

Ex:

public function method1() {
    // method content ...
    return $this;
}

public function method2() {
    // method content ...
    return $this;
}

Please refer the following link to read more on Method Chaining,

http://www.techflirt.com/tutorials/oop-in-php/php-method-chaining.html

There will be more articles you could find on this.

Answer 2

You need to return the object you want to chain the next method to.

public function chain() {
    return $this;
}

Sometimes this will be the current class ($this), somethings this will be an instance of another class depending on what is appropriate.