Pass a function by reference in PHP

Question

Is it possible to pass functions by reference?

Something like this:

function call($func){
    $func();
}

function test(){
    echo \"hello world!\";         


        

Answer 1

A similar pattern of this Javascript first class function:

function add(first, second, callback){
    console.log(first+second);
    if (callback) callback();
}

function logDone(){
    console.log('done');
}

function logDoneAgain(){
    console.log('done Again');
}
add(2,3, logDone);
add(3,5, logDoneAgain);

Can be done in PHP (Tested with 5.5.9-1ubuntu on C9 IDE) in the following way:

// first class function
$add = function($first, $second, $callback) {
  echo "\n\n". $first+$second . "\n\n";
  if ($callback) $callback();
};

function logDone(){
  echo "\n\n done \n\n";
}
call_user_func_array($add, array(2, 3, logDone));
call_user_func_array($add, array(3, 6, function(){
  echo "\n\n done executing an anonymous function!";
}));

Result: 5 done 9 done executing an anonymous function!

Reference: https://github.com/zenithtekla/unitycloud/commit/873659c46c10c1fe5312f5cde55490490191e168