这里有两种可能性:

1. 在页面开头使用 session_start(); 启动会话.

2. 使用以下代码:

1. Start the session by using session_start(); at the begining of page.

2. use the following code:

$accessquery = mysqli_query($conn, "SELECT roleid FROM person WHERE email = '". $email ."'", mysqli_store_result($conn));

$access = mysqli_fetch_row($accessquery);

$_SESSION['Access'] = $access[0];