PHP 生成唯一激活码

<?php
/**
 * 从来没有产生一个唯一的激活码
 * @return string
 */
function create_guid($namespace = null) {
	static $guid = '';
	$uid = uniqid ( "", true );
	
	$data = $namespace;
	$data .= $_SERVER ['REQUEST_TIME']; 	// 请求那一刻的时间戳
	$data .= $_SERVER ['HTTP_USER_AGENT']; 	// 获取訪问者在用什么操作系统
	$data .= $_SERVER ['SERVER_ADDR']; 		// serverIP
	$data .= $_SERVER ['SERVER_PORT']; 		// port号
	$data .= $_SERVER ['REMOTE_ADDR']; 		// 远程IP
	$data .= $_SERVER ['REMOTE_PORT']; 		// port信息
	
	$hash = strtoupper ( hash ( 'ripemd128', $uid . $guid . md5 ( $data ) ) );
	$guid = '{' . substr ( $hash, 0, 8 ) . '-' . substr ( $hash, 8, 4 ) . '-' . substr ( $hash, 12, 4 ) . '-' . substr ( $hash, 16, 4 ) . '-' . substr ( $hash, 20, 12 ) . '}';
	
	return $guid;
}

//使用
echo $key = create_guid ();