blend two colours in PHP

gistfile1.txt

/**
 *
 * $color1 - hexdecimal color 1 without the hash at the beginning e.g. ffffff
 * $color2 - hexdecimal color 1 without the hash at the beginning e.g. 000000
 * $ratio - ration between the two colors as a fraction of 1 e.g. for 65% use 0.65 
 *
 **/
function mix_colors_blend($color1, $color2, $ratio = 0.5) {
  $color1_red   = hexdec(substr($color1, 0, 2));
  $color1_green = hexdec(substr($color1, 2, 2));
  $color1_blue  = hexdec(substr($color1, 4, 2));

  $color2_red   = hexdec(substr($color2, 0, 2));
  $color2_green = hexdec(substr($color2, 2, 2));
  $color2_blue  = hexdec(substr($color2, 4, 2));

  $color1_ratio = $ratio;
  $color2_ratio = 1 - $ratio;

  $newcolor_red   = (($color1_red * $color1_ratio   + $color2_red * $color2_ratio));
  $newcolor_green = (($color1_green * $color1_ratio + $color2_green * $color2_ratio));
  $newcolor_blue  = (($color1_blue * $color1_ratio  + $color2_blue * $color2_ratio));

 return dechex($newcolor_red).dechex($newcolor_green).dechex($newcolor_blue);
}