Question

What is the utility of requiring the $this-> before calling a method from within its own (or a child’s) class? What is this meant to prevent? Wouldn’t it be logical to think that the engine should look within the class by default?

Answer 1

Consider the following example:

function bar()
{
    echo "Outside\n";
}

class foo
{
    public function __construct()
    {
        bar();
    }

    public function bar()
    {
        echo "Inside\n";
    }
}

new foo;

So, without $this-> prefixing the constructor’s call to bar(), PHP calls the outside function and not the method. Using $this-> eliminates the ambiguity and precisely defines which function you want to call.

If what you have suggested were true (auto searching the class), then as far as I know (waiting for crazy unreadable hack in comments), it would be impossible in PHP for a class method to call a function in the global scope that has the same name as another class method.