isset函数不从其他页面传递变量

here i am getting a value from previous page with form here i assign the value to php variable $foodid i want to echo its value after the continue button is clicked

//its value is passed from the previous page form with action to this page
$foodid   =  $_REQUEST['foodid'];
//as soon as continue button is clicked i want to display $foodid
<form method="post" action="">
<input type="submit" name="continue" value="continue">
</form>
if(isset($_POST['continue'])){
echo $foodid;//here the foodid variable must be declared
}

PHP is a server side languaue

JAVASCRIPT - is a client side language

After redirecting to new page , you have the value with your self, but displaying it on click is possible with javascript only (will display the number without refreshing the page)

in PHP - its not impossible, but it does not make sense to redirect to same page with some additional parameters's to display

eg; on click continue , submit a form with no action and there form should have that input field with value which you want to display (can be in hidden type), it will get submitted to same page and you will get your value using

$_REQUEST['field_name'];

But its not recommended , use JS for this, people purposely use JS for such kind of things

You should pass the $foodid value through form to the php page. This can be done by declaring a hidden variable and assigning foodid value to it.

Try this

<?php
    $foodid   =  $_REQUEST['foodid'];
    ?>

    <form method="post" action="">
    <input type="hidden" value="<?php echo $foodid ?>"
    <input type="submit" name="continue" value="continue">
    </form>

    <?php
    if(isset($_POST['continue'])){
    echo $foodid = $_POST['foodid'];
    }