Question

I recently really wanted to us anonymous functions in PHP. Unfortunately my host is still on 5.2. I automatically thought this would work:

uasort($array, function($a, $b) {
    return $a > $b;
});

Is this how they work? Simply passed in as an argument instead of a callback? The docs don’t say specifically that’s how they do, but I have a working knowledge of JavaScript’s anonymous functions, so I assumed they would.

Answer 1

Yes. You can use it in place of regular PHP callbacks.

Try this (in PHP 5.3):

function wait($callback)
{
    sleep(10);
    call_user_func($callback);
}

wait(function(){
    echo "Hello!";
});

How call_user_func() works is it will accept any of the following:

'functionName'
array('className', 'methodName')
array($objectInstance, 'methodName');

and now in PHP 5.3

function(){ // .. do something .. 
}

My guess is that internal PHP functions user call_user_func() for callbacks, and because it has support for anonymous functions, they will work just as well as other callbacks.