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Pass javascript variable to php with ajax and the result doesn't show anything

This is my code and i want to pass javascript variable with ajax to php when i click submit button then the result doesn't show var_data variable from javascript What code is wrong? This is edit order one before everybody help me

 <!DOCTYPE html>
<html>
<head>

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js"></script>
<script>
        $(document).ready(function() {
            $('#sub').click(function() {
                var var_data = "Hello World";
                $.ajax({
                    url: 'http://localhost/ajax/PassVariable.php',
                    type: 'GET',
                     data: { var_PHP_data: var_data },
                     success: function(data) {
                         // do something;

                     }
                 });
             });
         });
 </script>

 </head>
 <body>

 <input type="submit" value="Submit" id="sub"/>

 <?php 
   $test = $_GET['var_PHP_data'];
     echo $test;
 ?>
 </body>
 </html>

and this is source code now

 <?php
     if (isset($_GET['var_PHP_data'])) {
       echo $_GET['var_PHP_data'];
     } else {
     ?>
     <!DOCTYPE html>
     <html>
       <head>
            <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7/jquery.js"></script> 
            <script src="http://malsup.github.com/jquery.form.js"></script> 
         <script>
             $(document).ready(function() {
                 $('#sub').click(function() {
                     var var_data = "Hello World";
                     $.ajax({
                         url: 'http://localhost/test.php',
                         type: 'GET',
                          data: { var_PHP_data: var_data },
                          success: function(data) {
                              // do something;
                             $('#result').html(data)
                          }
                      });
                  });
              });
         </script>
       </head>
       <body>
         <input type="submit" value="Submit" id="sub"/>
         <div id="result">
       </body>
     </html>
    <?php } ?>

this statement if(isset($_GET['var_PHP_data'])) output false and then show Hello World What should i do to do for isset($_GET['var_PHP_data']) is true?

Your solution has PHP issues: you don't check if the data exists, and also, you don't do anything with the result. I've modified the script to do the following:

  1. Check if the var_PHP_data var is set (in PHP, on the server).
  2. If yes, just send a blank text response containing that data.
  3. If no, then draw the form and everything else.
  4. In the form, I've created a #result div.
  5. Ajax response will be shown in this div.

Also make sure that you host the script at localhost and that it is called test.php. To make sure this is resilient, you can change the Ajax URL to <?php echo $_SERVER['PHP_SELF'];?> to make sure that you'll hit the correct script.

<?php
    if (isset($_GET['var_PHP_data'])) {
      echo $_GET['var_PHP_data'];
    } else {
    ?>
    <!DOCTYPE html>
    <html>
      <head>
        <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js">
        <script>
            $(document).ready(function() {
                $('#sub').click(function() {
                    var var_data = "Hello World";
                    $.ajax({
                        url: 'http://localhost/test.php',
                        type: 'GET',
                         data: { var_PHP_data: var_data },
                         success: function(data) {
                             // do something;
                            $('#result').html(data)
                         }
                     });
                 });
             });
        </script>
      </head>
      <body>
        <input type="submit" value="Submit" id="sub"/>
        <div id="result">
      </body>
    </html>
    <?php } ?>

Try jQuery Form its this will help to solve many problems.

For you question: try url without domain name, add tags 'form', change event click to submit, add data type

what are the contents of PassVariable.php ? if is the same where you have they jquery bit wont work coz php will print all the page again, if the file is different try

success: function(data) {
                     alert('databack = '+ data);

                 }

Try placing your input into a form and attaching the ajax call to the form onsubmit event. The way it happens in the provided happen is when you click in the field, in which case it submits before you can write anything really.

$(document).ready(function() {
        $('#brn').click(function() {
            var var_data = "Hello World";
            alert("click works");
            $.ajax({
                url: 'http://localhost/ajax/PassVariable.php',
                type: 'GET',
                 data: { x: var_data },
                 success: function(data) {
                     alert(data);

                 }
             });
         });
     });

change it to this code

then in PassVariable.php put

make button

<input type="button" id="btn"  value="click me" />

it should work because it is very basic example. If it doesn't work check your console if there are any JavaScript errors and remove them.

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