/**
 * Display memory useage
 *
 * @example
 * $before = get_memory_usage();
 * // run the function/whatever
 * // Then echo the function and drop the value from {$before} in it
 * echo get_memory_usage( $before );
 *
 * @param (integer) $before | The memory useage before the tracked function
 * @return (string) $result | The needed memory
 */
function get_memory_usage( $before = '' )
{
    $mem_usage = memory_get_usage( true ) - $before;

    // return plain integer if before the tracked function
    if ( empty ( $before ) )
        return $mem_usage;

    // prepare output for easier reading
    if  ( $mem_usage < 1024 )
    {
        $result = $mem_usage.' bytes';
    }
    elseif ( $mem_usage < 1048576 )
    {
        $result = round( $mem_usage / 1024,2 ).' kB';
    }
    else
    {
        $result = round( $mem_usage / 1048576,2 ).' MB';
    }

    return $result;
}