将$ this变量作为参数传递

Question

I need help in understanding the following php code.

    $this->_PageHeader = new PAGE_HEADER($this);

I want to understand the functionality of $this argument in PAGE_HEADER($this).

I knew that $this is used inside a class to refer property and methods but in this case, what values will be passed through this argument.

Answer 1

$this contains the current instance of the class you are in. So it means that you pass the current object of the class containing the code $this->_PageHeader = new PAGE_HEADER($this); to the constructor of the class PAGE_HEADER.

For instance:

class A 
{
    public $value = 1;

    public function execute()
    {
        $b = new B($this);
    }
}

class B
{
    public $value = 2;

    public function __construct(A $dep)
    {
        echo $dep->value; // 3
        echo $this->value; // 2
    }
}

$a = new A();
$a->value = 3;
$a->execute(); // In this execution, $this is the object $a.

This code will output 32.