Echo isn't working within a section of my PHP

Question

Okay, so I am trying to display text when something goes wrong. I want to have it so that if the page number is too high (above 3 in my case) it will display an error. Disregard the accessing mySQL database.

<?php
    function get($name)
    {
        return isset($_REQUEST[$name]) ? $_REQUEST[$name] : '';
    }

    function is_valid_index($index,$array)
    {
        return $index >= 0 && $index < count($array);

    }
?>




<?php

    //Variables

$dbhost = "localhost";
$dbuser = "admin";
$dbpass = "pass";
$dberror = "You have failed to connect to the database!";

$conn = mysqli_connect($dbhost,$dbuser,$dbpass) or die ($dberror);

$select_db = mysqli_select_db($conn, "database") or die ("Couldn't Select Database");
?>

<form>
<?php
        $page = array('Select List','Users', 'Groups');

        echo '<select name="Lists">';
            for($i = 0;
            $i < count($page);
            $i++)
            {
                echo '<option value="'.($i + 1).'">'.$page[$i].'</option>';
            }
        echo '</select>';
?>
    <input type='submit'>
    </form>
<?php
    if(get('page'))
    {
            $page_id = get('page');
            if(is_valid_index($page_id-1,$page))
            {
                echo "You have selected".$page[$page_id-1];
            }
            else
            {
                echo '<span style="color:red">Invalid Page</span>';
            }
    }
?>

Got the tutorial from this video: https://www.youtube.com/watch?v=SaRh2HauIXY

Answer 1

更改此

<div class="wrapper">
    <div class="box-content">
        <div class="fixed-element">

        </div>
    </div>
</div>

<style type="text/css">

    .wrapper {
        transform: translateX(50px);
        background: pink;
    }

    .box-content {
        height: 1000px;
        background: green;
    }

    .fixed-element{
        position: fixed;
        top: 0;
        left: 0;
        width: 50px;
        height: 50px;
        background: blue;
    }

</style>

进入这个

echo '<select name="Lists">';    

这样，函数echo '<select name="page">'; 将返回get('page')，true块将会执行，您的if调用也会执行