array_map example

index.php

<?php

  function multiply($x = array(), $y = 2)
	{
		$multiplier = function($value) use ($y) {
			return $value * $y;
		};
		$x = array_map($multiplier, $x);
		
		return $x;
	}
	
	$x = array(1,2,3,4);
	$x = multiply($x, 3);
	var_dump($x);