将32位md5压缩成8位32进制生成8位长度的唯一英文数字组合字符串

/*将32位MD5值压缩成8位32进制生成8位长度的唯一英文数字组合字符串*/

function num16to32($a){
	for($a = md5( $a, true ),
		$s = '0123456789ABCDEFGHIJKLMNOPQRSTUV',
		$d = '',
		$f = 0;
		$f < 8;
		$g = ord( $a[ $f ] ),
		$d .= $s[ ( $g ^ ord( $a[ $f + 8 ] ) ) - $g & 0x1F ],
		$f++
	);
	return $d;
}
echo num16to32('c4ca4238a0b923820dcc509a6f75849b');