Wrap a function inside another function

function_wrapping.php

<?php

function func_wrap($fn, $wrapper)
{
    // Unify calling of the wrapped function
    if(is_array($fn) or is_string($fn)) {
        $original = function() use ($fn) {
            return call_user_func_array($fn, func_get_args());
        };
    } else {
        $original = $fn;
    }
    
    $wrapped = function() use ($original, $wrapper) {
        $args = func_get_args();
        array_unshift($args, $original);
        return call_user_func_array($wrapper, $args);
    };
    
    return $wrapped;
}

$a = function() {
	return 1;
};

$b = func_wrap($a, function($original) {
	return $original() + 2;
});

echo $b(); // -> 3