Use this function to convert a hexa decimal color code to its RGB equivalent. Unlike many other functions provided here, it will work correctly with hex color short hand notation.
Also, if a proper hexa decimal color value is given (6 digits), it uses bit wise operations for faster results.
For eg: #FFF and #FFFFFF will produce the same result
<?php
/**
 * Convert a hexa decimal color code to its RGB equivalent
 *
 * @param string $hexStr (hexadecimal color value)
 * @param boolean $returnAsString (if set true, returns the value separated by the separator character. Otherwise returns associative array)
 * @param string $seperator (to separate RGB values. Applicable only if second parameter is true.)
 * @return array or string (depending on second parameter. Returns False if invalid hex color value)
 */ 
function hex2RGB($hexStr, $returnAsString = false, $seperator = ',') {
 $hexStr = preg_replace("/[^0-9A-Fa-f]/", '', $hexStr); // Gets a proper hex string
 $rgbArray = array();
 if (strlen($hexStr) == 6) { //If a proper hex code, convert using bitwise operation. No overhead... faster
 $colorVal = hexdec($hexStr);
 $rgbArray['red'] = 0xFF & ($colorVal >> 0x10);
 $rgbArray['green'] = 0xFF & ($colorVal >> 0x8);
 $rgbArray['blue'] = 0xFF & $colorVal;
 } elseif (strlen($hexStr) == 3) { //if shorthand notation, need some string manipulations
 $rgbArray['red'] = hexdec(str_repeat(substr($hexStr, 0, 1), 2));
 $rgbArray['green'] = hexdec(str_repeat(substr($hexStr, 1, 1), 2));
 $rgbArray['blue'] = hexdec(str_repeat(substr($hexStr, 2, 1), 2));
 } else {
 return false; //Invalid hex color code
 }
 return $returnAsString ? implode($seperator, $rgbArray) : $rgbArray; // returns the rgb string or the associative array
} ?>

OUTPUT:
hex2RGB("#FF0") -> array( red =>255, green => 255, blue => 0)
hex2RGB("#FFFF00) -> Same as above
hex2RGB("#FF0", true) -> 255,255,0
hex2RGB("#FF0", true, ":") -> 255:255:0