too long

/school
/teacher
  index.php
/student
  index.php

How can I call student/index.php from teacher/index.php?

in your teacher/index.php write

header("Location: ../student/index.php"); // this is incase you want to go to that page
require_once('../student/index.php'); // incase you want to include that file
require '../student/index.php';

This will 'call' the script. If the script has a return value, then simply make an assignment statement on the left side of the require statement.

$ret = require '../student/index.php';

In your teacher/index.php use this code at top

header("Location: ../student/index.php");

You can also use pecl_http (if available) and the function http_redirect.

http://php.net/manual/en/function.http-redirect.php