PHP使用<select>更改内容

Question

I have select menu and I want to change content when I change values like jquery but with php. I find this in answers but it doesn't work.

<?php
$page = null;
if(isset($_POST['page'])){
$page = $_POST['page'];
}
switch($page){
case 'page3': include_once('/path/to/page3content.php'); break;
case 'page2': include_once('/path/to/page2content.php'); break;
case 'page1': include_once('/path/to/page1content.php'); break;
default: include_once('/path/to/defaultcontent.php'); break;
}
?>
<form name="myform" action="" method="post">
<select name="page" onchange="this.form.submit()">
    <option value="page1"<?php if($page == "page1"){ echo " selected"; }?>>Page 1</option>
    <option value="page2"<?php if($page == "page2"){ echo " selected";}?>>Page 2</option>
    <option value="page3"<?php if($page == "page3"){ echo " selected";}?>>Page 3</option>
</select>

EDIT: The problem was in my browser. Now content is show before my form I want content to show after </select> How to do this?

Answer 1

if you want to show content after select then update this code

 <?php
session_start();
$page = null;
if (isset($_POST['page'])) {
    $page = $_POST['page'];
    $_SESSION['page'] = $page;
} else {
    $page = $_SESSION['page'];
}

?>
    <form name="myform" action="" method="post">
        <select name="page" onchange="this.form.submit()">
            <option value="page1"<?php if ($page == "page1") {
                echo " selected";
            } ?>>Page 1
            </option>
            <option value="page2"<?php if ($page == "page2") {
                echo " selected";
            } ?>>Page 2
            </option>
            <option value="page3"<?php if ($page == "page3") {
                echo " selected";
            } ?>>Page 3
            </option>
        </select>
    </form>

<?php
switch ($page) {
    case 'page3':
        include_once('/path/to/page3content.php');
        break;
    case 'page2':
        include_once('/path/to/page2content.php');
        break;
    case 'page1':
        include_once('/path/to/page1content.php');
        break;
    default:
        include_once('/path/to/defaultcontent.php');
        break;
}
?>