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         


        

Answer 1

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);

Answer 2

With PHP 7 you can use the nicer variable-function syntax everywhere. It works with static/instance functions, and it can take an array of parameters. More info at https://trowski.com/2015/06/20/php-callable-paradox

$ret = $callable(...$params);

Answer 3

When using namespaces, call_user_func() is the only way to run a function you don't know the name of beforehand, for example:

$function = '\Utilities\SearchTools::getCurrency';
call_user_func($function,'USA');

If all your functions were in the same namespace, then it wouldn't be such an issue, as you could use something like this:

$function = 'getCurrency';
$function('USA');

Edit: Following @Jannis saying that I'm wrong I did a little more testing, and wasn't having much luck:

<?php
namespace Foo {

    class Bar {
        public static function getBar() {
            return 'Bar';
        }
    }
    echo "<h1>Bar: ".\Foo\Bar::getBar()."</h1>";
    // outputs 'Bar: Bar'
    $function = '\Foo\Bar::getBar';
    echo "<h1>Bar: ".$function()."</h1>";
    // outputs 'Fatal error: Call to undefined function \Foo\Bar::getBar()'
    $function = '\Foo\Bar\getBar';
    echo "<h1>Bar: ".$function()."</h1>";
    // outputs 'Fatal error: Call to undefined function \foo\Bar\getBar()'
}

You can see the output results here: https://3v4l.org/iBERh it seems the second method works for PHP 7 onwards, but not PHP 5.6.

Answer 4

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 5

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 6

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.