php - 不同环境中的php会话变量将不起作用

Question

以下脚本适用于 windows xampp, php 5.3.8

session_start();
    if (empty($_SESSION['myvar']) && empty($_GET['myvar'])) {
        $myvar = "some_value";
    } elseif (!empty($_GET['myvar'])) {
        $_SESSION['myvar'] = $_GET['myvar'];
    }
    $_SESSION['myvar'] = $myvar;

但在 ubuntu 服务器上，如果我var_dump($myvar)的值为php 5.3.10null

Answer 1

您是否考虑过您可能会定义会话变量两次，覆盖 if 语句中定义的第一个变量？此外，如果您在 !empty($_GET['myvar']) 为真时运行以下代码：

session_start();
if (empty($_SESSION['myvar']) && empty($_GET['myvar'])) {
    $myvar = "some_value";
} elseif (!empty($_GET['myvar'])) {
    $_SESSION['myvar'] = $_GET['myvar'];
}
$_SESSION['myvar'] = $myvar;

您很可能会收到未定义的变量警告，因为您没有设置 $myvar. 尝试这个：

session_start();
if (empty($_SESSION['myvar']) && empty($_GET['myvar'])) {
    $myvar = "some_value";
    $_SESSION['myvar'] = $myvar;
} elseif (!empty($_GET['myvar'])) {
    $_SESSION['myvar'] = $_GET['myvar'];
}

Answer 2

$myvar仅当 session 或 get 参数为空时才添加值。否则为空。这个怎么样：

session_start();
$my_var = isset($_SESSION['my_var'] ? $_SESSION['my_var'] : 'default_value';
if(empty($_SESSION['myvar']) && empty($_GET['myvar'])){
    $myvar = 'some_value';
} elseif(!empty($_GET['my_var'))) {
    $myvar = $_GET['myvar'];
}
$_SESSION['my_var'] = $myvar;

或者简单地说：

session_start();
$_SESSION['my_var'] = isset($_GET['my_var']) ? $_GET['my_var'] : (isset($_SESSION['my_var']) ? $_SESSION['my_var'] : 'default_value');

Answer 3

empty($_SESSION['myvar']) && empty($_GET['myvar'])

一直都是假的。因为第一次 $_SESSION['myvar'] 为空，而 $_GET['myvar'] 不为空：</p>

$_SESSION['myvar'] = $myvar; // now $myvar is empty



 if (empty($_SESSION['myvar']) && empty($_GET['myvar'])) {
        $_SESSION['myvar'] = "some_value";
    } elseif (!empty($_GET['myvar'])) {
        $_SESSION['myvar'] = $_GET['myvar'];
    }