Why Do Forms Inside a $.load() Call Fail to Post Correctly, and How Can AJAX Solve This?

Form Inside of $.load Not Posting Correctly? A Detailed Explanation of the Issue

It's common to encounter situations where forms embedded within an area loaded via $.load fail to post data correctly. The crux of the problem lies in the asynchronous nature of $.load, which loads content into a specific element without reloading the entire page. This can lead to a discrepancy between the form's target action and the actual URL where the page resides.

To illustrate the issue, let's consider an example:

<pre class="brush:php;toolbar:false">
    Readthis = "MonsterRequest.php?id=<?php echo $_REQUEST['id']; ?>&amp;Mon=";
    TestVar = TestVar.replace(/\s/g, "");
    Readthis = Readthis + htmlencode(TestVar);
    $('#CenterPiece').load(Readthis); 

In this example, when a button is clicked, it executes code that loads content from "MonsterRequest.php" into an element with the ID "CenterPiece." However, because $.load is asynchronous, the form submission occurs before the content of "MonsterRequest.php" is fully loaded. This means that the form is submitted to the current page's URL, rather than to the intended target URL specified in its action attribute.

Understanding AJAX and How It Resolves the Issue

To resolve the issue, it's necessary to employ AJAX (Asynchronous JavaScript and XML). AJAX allows web pages to communicate with servers asynchronously, without reloading the entire page. This ensures that forms embedded within dynamically loaded content can submit data correctly to the intended target.

In essence, AJAX allows you to send data to a PHP file on the server, process the data, and return a response without reloading the page. The workflow is as follows:

File #1:

<pre class="brush:php;toolbar:false">
    <script>
        $(document).ready(function() {
            $('#Sel').change(function() {
                var opt = $(this).val();
                $.ajax({
                    type: "POST",
                    url: "receiving_file.php",
                    data: 'selected_opt=' + opt,
                    success:function(data){
                        alert('This was sent back: ' + data);
                    }
                });
            });
        });
    </script>

In this script, when the "Sel" dropdown changes, it triggers an AJAX request. The request is sent to "receiving_file.php" and contains the selected option's value.

File #2: receiving_file.php

<pre class="brush:php;toolbar:false">
    <?php
        $recd = $_POST['selected_opt'];
        echo 'You chose: ' . $recd;
    

In this PHP file, the received data is stored in the $recd variable, and a response is echoed back to the client.

Result:

When the option is changed in "File #1," an AJAX request is made to "File #2." The data is processed, and a response is sent back to the client without reloading the page.

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