samhuri.net


By Sami J. Samhuri

Class method? Instance method? It doesn't matter to PHP

Update: This has been discussed for PHP6. A little late, but I guess better than never.

I made a mistake while I was coding, for shame! Anyway this particular mistake was that I invoked a class method on the wrong class. The funny part was that this method was an instance method in the class which I typed by mistake. In the error log I saw something like "Invalid use of $this in class function."

I knew for a fact I hadn't used $this in a class method, so it was kind of a confusing error. I went to the file in question and found out that it was calling an instance method as a class method. Now that is some crazy shit.

I would fully expect the PHP parser to give me an error like "No class method [foo] in class [blah]", rather than try and execute it as a class method. The syntax is completely different; you use :: to call a class method and -> to call an instance method. And you use the name of a class when you call a class method.

This code:


class Foo {
  public static function static_fun()
  {
    return "This is a class method!\n";
  }

  public function not_static()
  {
    return "This is an instance method!\n";
  }
}

echo '<pre>';
echo "From Foo:\n";
echo Foo::static_fun();
echo Foo::not_static();
echo "\n";

echo "From \$foo = new Foo():\n";
$foo = new Foo();
echo $foo->static_fun();
echo $foo->not_static();
echo '</pre>';

Produces:


From Foo:
This is a class method!
This is an instance method!

From $foo = new Foo():
This is a class method!
This is an instance method!

What the fuck?! http://www.php.net/manual/en/language.oop5.static.php is lying to everyone.