php自定义session存储路径

1、找到php.ini配置文件，找到session.save_path，修改如下：

其中2表示session存储的目录深度，也就是分目录，避免一个目录下文件太多，造成IO负担。
session.save_path = "2;D:\xxx\php54\session"

2、如上设置后，重启apache后，在php文件session_start()后会报错。
Warning: session_start(): open(D:\xxx\php54\session\b\9\sess_b9h5uo3bra9j28f4p4rim8mg02, O_RDWR) failed: No such file or directory (2) in D:\wwwroot\test\index.php on line 2
Warning: Unknown: open(D:\xxx\php54\session\b\9\sess_b9h5uo3bra9j28f4p4rim8mg02, O_RDWR) failed: No such file or directory (2) in Unknown on line 0
Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (2;D:\xxx\php54\session) in Unknown on line 0

3、原来是session下的\b\9目录需要手动创建，所以写了一个函数。
<?php
function createSessionDir($sessionPath = '') {
    if(empty($sessionPath)) {
        return false;
    }
    $dirNameArr = array_merge(range(0, 9), range('a', 'z'));
    $sessionPath = rtrim($sessionPath, '\/') . DIRECTORY_SEPARATOR;
    foreach ($dirNameArr as $dirName) {
        $dirPath = $sessionPath . $dirName . DIRECTORY_SEPARATOR;
        foreach ($dirNameArr as $subDirName) {
            @mkdir($dirPath . $subDirName, 0777, true);
        }
    }
}

createSessionDir('D:\xxx\php54\session');