PHP: Variable in a function name

Question

I want to trigger a function based on a variable.

function sound_dog() { return 'woof'; }
function sound_cow() { return 'moo'; }

$animal = 'cow';
print sound_{$animal}(); *

The * line is the line that's not correct.

I've done this before, but I can't find it. I'm aware of the potential security problems, etc.

Anyone? Many thanks.

Answer 1

http://php.net/manual/en/functions.variable-functions.php

To do your example, you'd do

$animal_function = "sound_$animal";
$animal_function();

Answer 2

You can do that, but not without interpolating the string first:

$animfunc = 'sound_' . $animal;
print $animfunc();

Or, skip the temporary variable with call_user_func():

call_user_func('sound_' . $animal);

Answer 3

You should ask yourself why you need to be doing this, perhaps you need to refactor your code to something like the following:

function animal_sound($type){ 
    $animals=array(); 
    $animals['dog'] = "woof"; 
    $animals['cow'] = "moo"; 
    return $animals[$type];
}

$animal = "cow";
print animal_sound($animal);

Answer 4

You can do it like this:

$animal = 'cow';
$sounder = "sound_$animal";
print ${sounder}();

However, a much better way would be to use an array:

$sounds = array('dog' => sound_dog, 'cow' => sound_cow);

$animal = 'cow';
print $sounds[$animal]();

One of the advantages of the array method is that when you come back to your code six months later and wonder "gee, where is this sound_cow function used?" you can answer that question with a simple text search instead of having to follow all the logic that creates variable function names on the fly.