PHP函数生成v4 UUID

从PHP手册上的此注释中，您可以使用以下代码：

function gen_uuid() {    return sprintf( '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',        // 32 bits for "time_low"        mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ),        // 16 bits for "time_mid"        mt_rand( 0, 0xffff ),        // 16 bits for "time_hi_and_version",        // four most significant bits holds version number 4        mt_rand( 0, 0x0fff ) | 0x4000,        // 16 bits, 8 bits for "clk_seq_hi_res",        // 8 bits for "clk_seq_low",        // two most significant bits holds zero and one for variant DCE1.1        mt_rand( 0, 0x3fff ) | 0x8000,        // 48 bits for "node"        mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff )    );}