在没有java / jquery的情况下更改页面标题[duplicate]

so my index page looks like this

<?php include 'header.php';?>
 <main id="main" role="main">
   <?php
    if ($_GET['page'] == "") {
        if ($_POST['page'] <> "") {
            $page = $_POST['page'];
            }
        else {
            $page = "homepage";
            }
        }
    else {
        $page = $_GET['page'];
        }

    switch($page) {
    case "about": include "about.php"; break;
    case "mission": include "mission.php"; break;
    ?>
  </main>
 <?php include 'footer.php';?>

The header got a standard title tag, my question is how can i change the title for each index.php?page=page-name

</div>

By the time your page check has started, header.php has already been interpreted. So there is no way to inject the title unless you put the page check above the title.

Additionally, since you're checking both GET and POST, you might consider simplifying your code as follows:

<?php

switch($_REQUEST['page']) {
    case "about":
        include "about.php";
        break;

    case "mission":
        include "mission.php";
        break;

    default:
        include "homepage.php";
}