PHP使用session_set_save_handler陷阱

陷阱如下

当脚本使用了session_set_save_handler 来重定向 session后，使用session_destroy后再使用session_start()重新开启session会报错

代码如下，

<?php
function open() {
    echo 'session start';
    echo "\n";
}

function close() {
    echo 'session close';
    echo "\n";
}

function read($sessionId) {
    echo 'read'.$sessionId;
    echo "\n";
}

function write($sessionId, $data) {
    echo 'write'.$sessionId.$data;
    echo "\n";
}

function destroy($sessionId) {
    echo 'destroy '.$sessionId;
    echo "\n";
}
function gc($lifetime) {
    echo 'gcccc';
    echo "\n";
}
session_set_save_handler('open', 'close', 'read', 'write', 'destroy', 'gc');
session_start();
echo session_id();
echo "\n";
session_destroy();

session_start();
$id = 'h06vgdfdfve6b8f66sva6basf8';
session_id($id);
echo session_id();

运行后报错

 Fatal error: session_start() [<a href='function.session-start'>function.session-start</a>]: Failed to initialize storage module: user (path: /var/lib/php/session) in /home/user/site/session.php on line 39

屏蔽session_set_save_handler('open', 'close', 'read', 'write', 'destroy', 'gc');

正常流程下（使用原生session）错误不会再出现。

so..

如果网站要使用自定义session建议自己封装和直接使用相关函数， 绕开session_set_save_handler