PHP 生成唯一的激活码

<?php /** * 生成永远唯一的激活码 * @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']; 	// 获取访问者在用什么操作系统	$data .= $_SERVER ['SERVER_ADDR']; 		// 服务器IP	$data .= $_SERVER ['SERVER_PORT']; 		// 端口号	$data .= $_SERVER ['REMOTE_ADDR']; 		// 远程IP	$data .= $_SERVER ['REMOTE_PORT']; 		// 端口信息		$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 ();