Method chaining is an advanced OOP concept in PHP. If you have experience in working with frameworks like CodeIgniter or CakePHP, you should have noticed a very convenient style of accessing different classes and methods and it looks something like this:

$obj->foo->bar->anotherMethod();

This technique in programming is known as method chaining. We’ll understand more about this fancy concept by the end of this blog post.

Method Chaining in Simple Class

class Music{
    private $artiste;
    private $genre;

    public function setArtiste($artiste){
        $this->artiste = $artiste;
    }

    public function setGenre($genre){
        $this->genre = $genre;
    }

    public function displayArtiste(){
      echo $this->artiste." belongs to the ".$this->genre. " genre.";
    }
}

To access the class, we’ll create an object of the Music class:

$band = new Music();
$band->setArtiste('Aerosmith');
$band->setGenre('Hard Rock');
$band->displayArtiste();

This example will print:

Aerosmith belongs to the Hard Rock genre.

Demo

Introducing Method Chaining

To enable method chaining in our previous example, we need to add only a single line of code in each 'setXXX' function. And that code is return $this;.

Now our class looks like:

class Music {
    private $artiste;
    private $genre;

    public
    function setArtiste($artiste) {
        $this - > artiste = $artiste;
        return $this; //Returns object of 'this' i.e Music class
    }

    public
    function setGenre($genre) {
        $this - > genre = $genre;
        return $this; //Again, returns object of 'this' i.e Music class
    }

    public
    function displayArtiste() {
        echo $this - > artiste.
        " belongs to the ".$this - > genre.
        " genre.";
    }
}

Now, we can finally access our class through fancy method chaining like this:

$band = new Music();
$band->setArtiste('Aerosmith')->setGenre('Hard Rock')->displayArtiste();

Demo

Explanation of Concept

Obvious, now you are slightly confused about what the f@#k is going on here. Let’s go through this code in baby steps. Before that, remember that method chaining in PHP always works from left to right.

$band = new Music() creates a new object in the Music class.

Then, $band->setArtiste('Aerosmith') assigns the name to a variable and returns the object of the same class. Now that $band->setArtiste('Aerosmith') has become an object of the Music class, so we can access the Music class by using $band->setArtiste('Aerosmith') as an object.

Next, we set the genre by using $band->setArtiste('Aerosmith')->setGenre('Hard Rock'). setGenre() again, returns the object of the class, so the complete phrase $band->setArtiste('Aerosmith')->setGenre('Hard Rock') is again, now an object of Music.

Lastly, we’ll print out the band’s information by accessing the displayArtiste() function:

$band->setArtiste('Aerosmith')->setGenre('Hard Rock')->displayArtiste();

And there you have it, basic method chaining.