$this variable in PHP

Question

Hello all,

I've just started getting familiarized with OO features of PHP, and I would like to ask you something about the $this variable. First of all, if a class that I'm using the $this keyword in does not have a defined property variable foo, does that mean that using the following code:

$this->foo = 5;
echo $this->foo;

will create the foo property on the object on runtime, like in JavaScript? What is the visibility of this property?

Answer 1

Yes, this will create the foo property, and its visibility will be public (which is the default).

You could test this quite easily:

<?php
class Foo {
    public function setFoo($foo) {
        $this->foo = $foo;
    }
}

$f = new Foo();
$f->setFoo(5);
echo $f->foo;

Will print 5 with no errors.

Answer 2

Yes it certainly will.

Answer 3

Properties can be added to any objects, independently of its class. It is also possible to write

<?php
$obj = new stdClass();
$obj->foo = 'bar';

Answer 4

Worth mentioning is the __get and __set magic function. Theese methods will be called whenever an undefined property is called.

This enables a way to create pretty cool and dynamic objects. Perfect for use with webservices with unknown properties.

Answer 5

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