Is there differences between call_user_func() and $var()?

Question

Is there any differences between call_user_func() and its syntactic sugar version...

// Global function

$a = 'max';

echo call_user_func($a, 1, 2); // 2
echo $a(1, 2); // 2

// Class method

class A {

   public function b() {
     return __CLASS__;
   }

   static function c() {
      return 'I am static!';
   }

}

$a = new A;
$b = 'b';

echo call_user_func(array($a, $b)); // A
echo $a->$b(); // A

// Static class method

$c = 'c';

echo call_user_func(array('A', $c)); // I am static!
echo a::$c(); // I am static!

codepad.

Both output the same, but I was recently hinted (10k+ rep only) that they are not equivalent.

So, what, if any, are the differences?

Pfft, "10k+ rep only". Quit bragging ;) – Phil Feb 21 '11 at 03:16 — Phil, Feb 21 '11 at 03:16

score 6 · Accepted Answer · answered Feb 21 '11 at 03:00

First difference I can think of is that call_user_func() runs method as a callback.

This means you can use a closure, eg

echo call_user_func(function($a, $b) {
    return max($a, $b);
}, 1, 2);

This would be more of an implementation difference versus a usage or performance (execution) one though.

score 6 · Answer 2 · answered Feb 21 '11 at 03:21

I honestly can't find much of a difference between the two. They basically do the same thing, but the only differences I can find is that call_user_func takes over 2× longer to complete than variable functions (calling an empty function).

Another thing is that the error handlers are different, if you use a non-existent callback function, the variable function would output a fatal error and halt the script while call_user_func would output a warning but continue the script.

Also when passing parameters through the function, using variable functions provides a little more detail in the error in relation to line numbers:

function asdf($a, $b) {
  return(1);
}

call_user_func('asdf', 1):

Warning: Missing argument 2 for asdf() in G:\test.php on line 3

-

$a='asdf'; $a($a, 1):

Warning: Missing argument 2 for asdf(), called in G:\test.php on line 10 and defined in G:\test.php on line 3

These errors are collected from Command-Line Interface (CLI) tests, the display of errors obviously depends on your configuration.

Is there differences between call_user_func() and $var()?

2 Answers2