PHP Adjust Colors

function adjustBrightness($hex, $steps) {
      // Steps should be between -255 and 255. Negative = darker, positive = lighter
	    $steps = max(-255, min(255, $steps));

	    // Format the hex color string
	    $hex = str_replace('#', '', $hex);
	    if (strlen($hex) == 3) {
	        $hex = str_repeat(substr($hex,0,1), 2).str_repeat(substr($hex,1,1), 2).str_repeat(substr($hex,2,1), 2);
	    }

	    // Get decimal values
	    $r = hexdec(substr($hex,0,2));
	    $g = hexdec(substr($hex,2,2));
	    $b = hexdec(substr($hex,4,2));

	    // Adjust number of steps and keep it inside 0 to 255
	    $r = max(0,min(255,$r + $steps));
	    $g = max(0,min(255,$g + $steps));  
	    $b = max(0,min(255,$b + $steps));

	    $r_hex = str_pad(dechex($r), 2, '0', STR_PAD_LEFT);
	    $g_hex = str_pad(dechex($g), 2, '0', STR_PAD_LEFT);
	    $b_hex = str_pad(dechex($b), 2, '0', STR_PAD_LEFT);

	    return '#'.$r_hex.$g_hex.$b_hex;
	}