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

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 2

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.