[RESOLVED] Static function causing local variable assignment (possible PHP bug?)

CrashRoX

You have two classes (Class1 and Class2). Class1 calls a non static
Class2 function with a Class2 variable assignment, but without a return
value. The value set in Class2 is somehow assigned to Class1. If the
function was set to static or the class is instantiated the problem does
not occur. See code example below for better explanation... I submitted a bug report to PHP, but maybe I was wrong and theres a logical explanation?

// Causes unexpected results
class Class1 {
public function __construct() {
Class2::dosomething();
}
}

class Class2 {

private $somevar;
public  function dosomething() {
	$this->somevar = 'test';
}

}

$x = new Class1();
print_r($x);

You should see:
Class1 Object ( )

But instead you see:
Class1 Object
(
[somevar] => test
)

laserlight

It seems to me that the bug is in your code. Why do you want to call Class2's dosomething() statically? What does it mean to call a method that uses the $this variable statically?

I would speculate that since there is no instance of Class2 by which 'test' can be assigned to $this->somevar, the PHP interpreter creates one under the hood, thus you see the member variable of this Class2 instance in your Class1 object.

CrashRoX

What you are saying makes perfect sense. Regardless of the coding "error", there is no reason why Class2 should assume it has access to $this from Class1. Seems like a scope error to me. I would think an error would be thrown saying something along the lines of: "Using $this when not in object context", no? If function dosomething was declared statically thats exactly what would happen.

laserlight

Regardless of the coding "error", there is no reason why Class2 should assume it has access to $this from Class1.

Actually, my speculation is the opposite: Class1 appears to have access to $this of Class2, under the hood.

In fact, looking at the PHP manual entry for OOP support for PHP4 shows that my speculation is reality:

Note: The $this pseudo-variable is not usually defined if the method in which it is hosted is called statically. This is not, however, a strict rule: $this is defined if a method is called statically from within another object. In this case, the value of $this is that of the calling object.

Nonetheless, note that in PHP5 "calling non-static methods statically generates an E_STRICT level warning", so I still think that it is something of a bug with your code example, not the PHP implementation itself.

CrashRoX

Functionally it is a bug in my code. I was aware of that, just wanted to understand why it functioned the way it did (I have since changed my code). Thank you for clearing that up.

laserlight

No problem 🙂
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