Function to invertRGBa values via PHP

invertRGBa.php

<?php
/*
 * Invert incoming RGB/RGBa CSS-String OR just values to RGBa values
 * Expects a string in one of the following formats:
 * 255, 255, 255, 0 // Just parameters with/without Alpha value
 * rgba(255,255,0) // Full CSS value  with/without Alpha value
 *
 * Thomas A. Reinert // www.tarthemems.com 2015
 */


function invertRGBa($rgba) {
    $rgba = trim(str_replace(' ', '', $rgba));
    if (stripos($rgba, 'rgba') !== false) {
        $res = sscanf($rgba, "rgba(%d, %d, %d, %f)");
    }
    else {
        $res = sscanf($rgba, "rgb(%d, %d, %d)");
        $res[] = 1;
    }
    $r = 255-$res[0];
    $g = 255-$res[1];
    $b = 255-$res[2];

    $output = "$r, $g, $b";
    if (isset($res[3] ,$res)) {
    	$output .= ", " . $res[3];
    } else {
    	$output .= ", 1";
    }
    return $output;
}

/*
 * Example Usages:
 */
// echo invertRGBa('255, 255, 255, 0'); // Returns: 255, 255, 255, 1

// echo invertRGBa('rgba(255,255,0)'); // Returns: 0, 0, 255, 1

// echo 'rgba(' . invertRGBa("rgba(0,255,0);") . ');'; // Returns: rgba(255, 0, 255, 1);

?>

May be overcomplicated but works like a charm ;)