Question

Wondering how the example below is actually working, and how one would be able to do something like dynamically. Using call_user_func or call_user_func_array doesn’t allow this to happen.

<?php
class Person
{
    public $name = "George";

    public function say_hi()
    {
            return ExtraMethods::hi();
    }
}

class ExtraMethods
{
    public function hi()
    {
            return "Hi, ".$this->name;
    }
}

$george = new Person();
echo $george->say_hi();
?>

this should result with:

Hi, George

Wondering why the instance method hi can be called not only statically (not surprised that this can happen in PHP), but why I am able to use $this

Answer 1

From the manual:

The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).

So, according to the second portion, by design. Keep in mind it uses the actual object instance in existance though (in other words, if you add public $name = "SomethingElse"; to ExtraMethods, the result would still be Hi, George).

Calling the method statically is not proper coding, but PHP forgives you, and issues only a Strict Error:

"Strict Standards: Non-static method ExtraMethods::hi() should not be called statically, assuming $this from incompatible context in ..."

Of course, in this instance, just passing the object as an argument would be far clearer and preferable.