Shouldn't $this refer to the current object?

Question

I'm learning the differences between self, static and this and ran across this example from php.net:

<?php
class A {
    private function foo() {
        echo "success!\n";
    }
    public function test() {
        $this->foo();
        static::foo();
    }
}

class B extends A {
   /* foo() will be copied to B, hence its scope will still be A and
    * the call be successful */
}

class C extends A {
    private function foo() {
        /* original method is replaced; the scope of the new one is C */
    }
}

$b = new B();
$b->test();
$c = new C();
$c->test();   //fails
?>

The result is

success!
success!
success!


Fatal error:  Call to private method C::foo() from context 'A' in /tmp/test.php on line 9

My question is this: when creating the new object C, shouldn't the call $this->foo(); call the newly replaced private function foo inside class C (and return an error since it's private)?

Interesting! However, isn't the error message exactly what you expect it to be? The script tries to call C:foo() whereas the scope is within A, rightfully failling because foo() is now private to C. Or am I not undestanding what you mean? — Félix Adriyel Gagnon-Grenier, Feb 26 '17 at 21:34

score 1 · Answer 1 · edited May 23 '17 at 12:31

You should use protected rather than public to get this behaviour.

This is covered in a lot of detail here: What is the difference between public, private, and protected?

A quick excerpt:

public scope to make that variable/function available from anywhere, other classes and instances of the object.

private scope when you want your variable/function to be visible in its own class only.

protected scope when you want to make your variable/function visible in all classes that extend current class including the parent class.

Shouldn't $this refer to the current object?

1 Answers1