PHP call_user_func vs. just calling function

Question

I'm sure there's a very easy explanation for this. What is the difference between this:

function barber($type){
    echo "You wanted a $type haircut, no problem\n";
}
call_user_func('barber', "mushroom");
call_user_func('barber', "shave");

... and this (and what are the benefits?):

function barber($type){
    echo "You wanted a $type haircut, no problem\n";
}
barber('mushroom');
barber('shave');

Thanks in advance.

Answer 1

in your first example you're using function name which is a string. it might come from outside or be determined on the fly. that is, you don't know what function will need to be run at the moment of the code creation.

Answer 2

the call_user_func option is there so you can do things like:

$dynamicFunctionName = "barber";

call_user_func($dynamicFunctionName, 'mushroom');

where the dynamicFunctionName string could be more exciting and generated at run-time. You shouldn't use call_user_func unless you have to, because it is slower.

Answer 3

Always use the actual function name when you know it.

call_user_func is for calling functions whose name you don't know ahead of time but it is much less efficient since the program has to lookup the function at runtime.

Answer 4

I imagine it is useful for calling a function that you don't know the name of in advance... Something like:

switch($value):
{
  case 7:
  $func = 'run';
  break;
  default:
  $func = 'stop';
  break;
}

call_user_func($func, 'stuff');

Answer 5

Although you can call variable function names this way:

function printIt($str) { print($str); }

$funcname = 'printIt';
$funcname('Hello world!');

there are cases where you don't know how many arguments you're passing. Consider the following:

function someFunc() {
  $args = func_get_args();
  // do something
}

call_user_func_array('someFunc',array('one','two','three'));

It's also handy for calling static and object methods, respectively:

call_user_func(array('someClass','someFunc'),$arg);
call_user_func(array($myObj,'someFunc'),$arg);