Using JavaScript to Submit the Form

Oct 13, 2025 by wbrum.org 59 views

Introduction

When it comes to handling form submissions on your website, you may want to process the form values in a custom script rather than relying on the default form action. This can be particularly useful when you need to perform complex validation or integration with third-party services like PayPal. In this article, we will explore how to send form values from a script in functions.php and not from the form on your website.

Understanding the Problem

Let's assume you have a form on your website that allows users to select either PayPal or wire transfer as their payment method. Depending on their selection, you want to process the form values in a custom script in functions.php. However, by default, the form will submit to the URL specified in the action attribute, which is likely to be a server-side script that handles the form data.

Using JavaScript to Submit the Form

One way to achieve this is by using JavaScript to submit the form to the custom script in functions.php. Here's an example of how you can modify your form to achieve this:

HTML Form

<form id="myForm" method="post">
  <!-- form fields here -->
  <input type="radio" name="payment_method" value="paypal"> PayPal
  <input type="radio" name="payment_method" value="wire-transfer"> Wire Transfer
  <button type="submit">Submit</button>
</form>

JavaScript Code

document.getElementById('myForm').addEventListener('submit', function(event) {
  event.preventDefault();
  var paymentMethod = document.querySelector('input[name="payment_method"]:checked').value;
  if (paymentMethod === 'paypal') {
    // submit form to custom script in functions.php
    document.getElementById('myForm').action = '/wp-admin/admin-ajax.php';
    document.getElementById('myForm').submit();
  } else if (paymentMethod === 'wire-transfer') {
    // submit form to custom script in functions.php
    document.getElementById('myForm').action = '/wp-admin/admin-ajax.php';
    document.getElementById('myForm').submit();
  }
});

In this example, we add an event listener to the form's submit event. When the form is submitted, we prevent the default form submission behavior using event.preventDefault(). We then get the value of the selected payment method using document.querySelector(). Depending on the selected payment method, we update the form's action attribute to point to the custom script in functions.php and submit the form using document.getElementById('myForm').submit().

Using WordPress AJAX to Submit the Form

Another way to achieve this is by using WordPress AJAX to submit the form to the custom script in functions.php. Here's an example of how you can modify your form to achieve this:

HTML Form

<form id="myForm" method="post">
  <!-- form fields here -->
  <input type="radio" name="payment_method" value="paypal"> PayPal
  <input type="radio" name="payment_method" value="wire-transfer"> Wire Transfer
  <button type="submit">Submit</button>
</form>

JavaScript Code

document.getElementById('myForm').addEventListener('submit', function(event) {
  event.preventDefault();
  var paymentMethod = document.querySelector('input[name="payment_method"]:checked').value;
  var formData = new FormData(document.getElementById('myForm'));
  $.ajax({
    type: 'POST',
    url: '/wp-admin/admin-ajax.php',
    data: formData,
    processData: false,
    contentType: false,
    success: function(response) {
      console.log(response);
    }
  });
});

In this example, we add an event listener to the form's submit event. When the form is submitted, we prevent the default form submission behavior using event.preventDefault(). We then get the value of the selected payment method using document.querySelector(). We create a new FormData object using the form's elements and submit it to the custom script in functions.php using the $.ajax() method.

Processing the Form Values in functions.php

Now that we have submitted the form values to the custom script in functions.php, we need to process the form values in the script. Here's an example of how you can modify your functions.php file to achieve this:

function process_form_submission() {
  if (isset($_POST['payment_method'])) {
    $paymentMethod = $_POST['payment_method'];
    if ($paymentMethod === 'paypal') {
      // process PayPal payment
      $paypalPayment = new PayPalPayment();
      $paypalPayment->processPayment();
    } else if ($paymentMethod === 'wire-transfer') {
      // process wire transfer payment
      $wireTransferPayment = new WireTransferPayment();
      $wireTransferPayment->processPayment();
    }
  }
}
add_action('wp_ajax_nopriv_process_form_submission', 'process_form_submission');
add_action('wp_ajax_process_form_submission', 'process_form_submission');

In this example, we define a function process_form_submission() that checks if the payment_method field is set in the form data. Depending on the selected payment method, we create an instance of the corresponding payment class and call its processPayment() method to process the payment.

Conclusion

Introduction

In our previous article, we explored how to send form values from a script in functions.php and not from the form on your website. We discussed two approaches: using JavaScript to submit the form to the custom script in functions.php and using WordPress AJAX to submit the form to the custom script in functions.php. In this article, we will answer some frequently asked questions about this topic.

Q: What is the difference between using JavaScript and WordPress AJAX to submit the form?

A: Using JavaScript to submit the form involves creating a custom JavaScript code that submits the form to the custom script in functions.php. On the other hand, using WordPress AJAX to submit the form involves using the $.ajax() method to submit the form to the custom script in functions.php. Both approaches can be used to submit the form to the custom script in functions.php, but WordPress AJAX provides a more robust and secure way to handle form submissions.

Q: How do I prevent the default form submission behavior when using JavaScript to submit the form?

A: To prevent the default form submission behavior when using JavaScript to submit the form, you can use the event.preventDefault() method. This method prevents the default action of the form submission and allows you to handle the form submission in your custom JavaScript code.

Q: How do I handle form validation when using WordPress AJAX to submit the form?

A: When using WordPress AJAX to submit the form, you can handle form validation by checking the form data in the $.ajax() method. You can use the $.ajax() method's data parameter to pass the form data to the custom script in functions.php. In the custom script, you can then check the form data and return an error message if the form data is invalid.

Q: How do I process the form values in the custom script in functions.php?

A: To process the form values in the custom script in functions.php, you can use the $_POST superglobal to access the form data. You can then use the form data to perform any necessary actions, such as processing a payment or sending an email.

Q: How do I secure the custom script in functions.php?

A: To secure the custom script in functions.php, you can use WordPress's built-in security features, such as nonce verification and capability checks. You can also use a secure protocol, such as HTTPS, to encrypt the form data and prevent eavesdropping.

Q: Can I use a plugin to handle form submissions instead of writing custom code?

A: Yes, you can use a plugin to handle form submissions instead of writing custom code. There are many plugins available that provide form submission handling functionality, such as Gravity Forms and Formidable Forms. However, using a plugin may limit your flexibility and customization options.

Q: How do I troubleshoot issues with form submissions?

A: To troubleshoot issues with form submissions, you can use the WordPress debug log to identify any errors or warnings that may be occurring. You can also use the browser's developer tools to inspect the form data and identify any issues with the form submission.

Conclusion

In this article, we answered some frequently asked questions about sending form values from a script in functions.php and not from the form on your website. We discussed the differences between using JavaScript and WordPress AJAX to submit the form, how to prevent the default form submission behavior, how to handle form validation, how to process the form values in the custom script, how to secure the custom script, and how to troubleshoot issues with form submissions. By following these tips and best practices, you can create a secure and reliable form submission system for your WordPress website.