Add PHP function

virtual tpv? Is that the same as virtual point of sale (virtual POS)? Where your app looks like a POS interface, but the transaction is relayed to an external payment gateway.

This box where you put the desired amount — is this one of the fields the gateway needs or is it used to calculate a different field? If it’s to calculate another field, you are probably looking at something in JavaScript, not PHP. When data is input on a form in a browser that will be sent directly to a gateway, it’s too late for PHP on your server to do anything. For PHP to be useful, the data needs to be known before the POS interface is sent out. Once sent out, you need JavaScript (or jQuery) to make changes to data.

Yes, it is a virtual point of sale, PayPal type but it is from the bank.

What I would have to do is, have a box where you can enter the amount to be charged and when you send it, put it in the PHP line that I said before and then PHP would do the job it has.

It is simply to have a box where to put the amount that is going to be charged and by clicking on the send button put that amount in the PHP so that it can do the function.

OK, but there is no PHP available where the box appears on the user’s browser. You could submit the value back to your server, where PHP can then get the sent value and configure a request to the payment gateway. Whether that’s the proper topology for your gateway, I could not say.

The other possibility is the browser submits the request directly to the gateway API. Then it relays the result to your server. I’m guessing it’s the former because then your API key can remain secret. Thus the form with the amount submits to a form/payment handling script on your server. This would indeed be PHP. Assuming the form method is POST, the amount submitted is in the $_POST array, keyed by the field’s name.

The PHP script can then configure and send a proper API request to the payment gateway. The script then loops, waiting for a response. The response is then handled as needed.

An important detail is exactly where and how the form submits to the server. If you do not need any WP resources, it can be any PHP file containing the form handling script. If you need WP resources to process the payment, your options are limited. The form could submit an Ajax request to wp-admin/admin-ajax.php instead of using the traditional form submit method. Or the form can submit to wp-admin/admin-post.php. This is similar to Ajax, but no jQuery is required. A normal POST request will be fine. The only other option is to submit to a WP page that’s based on a custom template capable of handling the form submittal.

Thank you very much for your response @bcworkz it has served me well. I will see the possibility of making the charges through another alternative or see if the fixed value can continue using it.

You’re welcome. I’m still not sure I fully understand what you are trying to do. I’m glad what I posted makes some sense. The fact remains anything a user enters into a form needs to be sent back to a server over HTTPS before PHP can do anything with it. There’s no way around that no matter what topology you are using.

If you are familiar with client scripting but new to server scripting, that important fact is not that obvious at first.