这是什么PHP语法？ （PhpStorm）

I've only seen this syntax once before and can't find it anywhere on the internet. Has anyone else seen Php syntax like this?

<?php
/**
* Created by PhpStorm.
* Date: 10/5/15
* Time: 3:11 PM
*/
$tag = $_POST['tag'];
$tag
->DIV(array(
    'id' => 'home' ,
) , $tag()
    ->DIV(array(
        'class' => 'headLine' ,
    )
    ) , $tag()
);

This code seems a chain method or fluent interface, every time you call the method DIV() it return itself.

<?php 

Class Element{
    private $elements = [];
    public function add($e){
        $this->elements[] = $e;
        return $this;
    }

    public function show(){
        echo '<pre>';
        print_r($this->elements);
    }
}


$e = new Element();

$e->add('<form action="register.php" method="post">')
        ->add('<input type="text" name="id" /> ')
        ->add('<input type="text" name="name" />')
        ->add('<input type="text" name="email" />')
        ->add('<input type="password" name="password" />')
        ->add('<input type="submit" name="send" />')
   ->add('</form>')
   ->show();