function_composing.php

<?php
// pipes each function's return value as input into the next function in the chain
function func_compose()
{
	$fns = func_get_args();
	
	$composition = function() use ($fns) {
		$input = func_get_args();
		foreach ($fns as $fn) {
			$return = call_user_func_array($fn, $input);
			$input  = array($return);
		}
		return $return;
	};
	
	return $composition;
}

$greet = function($name) {
	return "Hello $name";
};

$exclaim = function($statement) {
	return $statement . '!';
};

$fn = func_compose($greet, $exclaim);
echo $fn("World"); // $exclaim($greet("World")) -> Hello World!