如何在php中使用javascript中的变量？

Question

I'm having a brain freeze at the moment.. I have a variable here in this bit of JavaScript code...

<script type="text/javascript">

    $('#menuNameEdit').val(reservationId);

</script>

I have managed to use #menuNameEdit in form input as below but I don't know how to use it as a normal variable in PHP. For example if I want to compare it's value against another variable. Mind Block!

<input id="menuNameEdit" name="reservationId" type="text" 
   class="form-control" disabled>

Answer 1

You can't. It's just not possible. If JS starts with its work, PHP is already done.

The only way to do that - though its extremely vulnerable - is via AJAX:

$.ajax({
    type: "POST",
    url: "your_php_script.php",
    data: {var: your_variable},
    success: function() {
        console.log("ajax successful!");
    }
});

Without jQuery:

var request = new XMLHttpRequest();
request.open('POST', 'your_php_script.php', true);
request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
request.send(your_variable);

This needs to be in your_php_script.php:

$jsVariable = $_POST['var'];

This is extremely vulnerable though - always sanitize input via filter_var() or htmlspecialchars() which could be modified by the user!

Answer 2

If your form gets submitted you can access the below code:

PHP

if(isset($_POST['reservationId'])){    
echo $_POST['reservationId'];    
}

HTML

<form method="" action="" id="form-id">
<input id="menuNameEdit" name="reservationId" type="text" class="form-control" disabled>
<input name="submit" type="submit" class="form-control">    
</form>

Jquery

var menuNameEdit = $('#menuNameEdit').val();

 $.ajax({
        type: "POST",
        url: "index.php",
        data: {menuNameEdit : menuNameEdit },
        success: function() {
            console.log("Success!");
        }
    });

index.php

echo $_POST['menuNameEdit'];

Answer 3

<?php
if (isset($_POST['submit'])) {
     $reservationId = $_POST['reservationId'];
     $reservationId2= $_POST['reservationId2'];

//comparison

}
?>   
 <form class='addcategory' method="post"    enctype="application/x-www-form-urlencoded">

       <input id="menuNameEdit" name="reservationId" type="text" 
   class="form-control" disabled>

<input id="another" name="reservationId2" type="text" 
   class="form-control"  >
<input name="submit" type="submit" value="submit">

</form>