从 $_SESSION 获取 var 会引发错误 - getting vars from $_SESSION throws an error

在传递$_SESSION['var']函数时，如果未设置$_SESSION['var']，我会收到通知：

Notice: Undefined index: var in scripname.php on line 49

有没有更安全的方法来获得$_SESSION['var']，如果$_SESSION['var']未设置，它会给我0？

提前谢谢你！！

$var = isset($_SESSION['var']) ? $_SESSION['var'] : 0

if (isset($_SESSION['var']))
{
    echo "session is set";
}
else
{
    echo "session is not set";
}

if (isset($_SESSION['var'])){
    // Do something
}

怎么样：

$var = @$_SESSION['var'];

if(!array_key_exists('var',$_SESSION))
{
    $var = 0;
}
else
{
    $var = $_SESSION['var'];
}

使用

if(isset($_SESSION['var']))
    // do