Converting certain values back and forth is often necessary when developing functions to help your website work the way you want it to. I needed a function that would convert a hex color to rgb and for some reason it took me a while to figure it out.

function hex2rgb($hex) {
   $hex = str_replace("#", "", $hex);

   if(strlen($hex) == 3) {
      $r = hexdec(substr($hex,0,1).substr($hex,0,1));
      $g = hexdec(substr($hex,1,1).substr($hex,1,1));
      $b = hexdec(substr($hex,2,1).substr($hex,2,1));
   } else {
      $r = hexdec(substr($hex,0,2));
      $g = hexdec(substr($hex,2,2));
      $b = hexdec(substr($hex,4,2));
   }
   $rgb = array($r, $g, $b);
   //return implode(",", $rgb); // returns the rgb values separated by commas
   return $rgb; // returns an array with the rgb values
}

This function works with both shorthand hex codes such as #f00 and longhand hex codes such as #ff0000. It also accepts the number sign (#) just in case. You can see there are two return lines at the end of the function. The first, which is commented out, will return the rgb values separated by a comma. The second, which is the default, will return an array with the rgb values.

So now with this function in place we can use it like so:

$rgb = hex2rgb("#cc0");
print_r($rgb);

The above function would output:

Array ( [0] => 204 [1] => 204 [2] => 0 )

Since we are going one way with this, might as well go the other. Here is a function to convert rgb to a hex color:

function rgb2hex($rgb) {
   $hex = "#";
   $hex .= str_pad(dechex($rgb[0]), 2, "0", STR_PAD_LEFT);
   $hex .= str_pad(dechex($rgb[1]), 2, "0", STR_PAD_LEFT);
   $hex .= str_pad(dechex($rgb[2]), 2, "0", STR_PAD_LEFT);

   return $hex; // returns the hex value including the number sign (#)
}

This function works like so:

$rgb = array( 255, 255, 255 );
$hex = rgb2hex($rgb);
echo $hex;

The above function would output:

#ffffff