Question

echo "<script>alert('登陆成功!');location.href='../main_teacher.php';</script>";

Answer 1

echo "<script>alert('登陆成功!');location.href='../main_teacher.php';</script>"
你的../什么鬼 你这里输出的是js语句了
你要的是上一级目录吧
你酌情修改
'main_teacher.php' 相同目录下
‘/main_teacher.php’ 根目录下 就是 http://xxxx.com/main_teacher.php
'/home/main_teacher.php' 就是 http://xxxx.com/home/main_teacher.php