This method basically goes through a string, gets the ASCII value of the character, multiplies it with the fraction of the character index divided by the overall length, and adds it to a total. It then appends the HEX value of the length of the string to the HEX value of this total.
// Example
str_uid(''); //191a78c
str_uid(''); //16177fa
str_uid('hey there!'); //a9998
str_uid(''); //00

function str_uid($str) {
	$uid = 0;
	for ($i = 1; $i < strlen($str); $i++) {
		$uid += round(ord($str[$i]) * ($i / strlen($str)), 2) * 100;
	return strval(dechex(strlen($str))).strval(dechex($uid));