How show a automatic message after submit a form - php

Question

I created a contact-form with username, email and a message.
Here is my code;
<form action="thanks.php" method="post">
<div>
<label for="nom">Nom :</label>
<input type="text" id="nom" name="user_name">
</div>
<div>
<label for="courriel">Courriel :</label>
<input type="email" id="courriel" name="user_email">
</div>
<div>
<label for="phone">Numéro de téléphone</label>
<input type="text" id="phone" name="phone_number">
</div>
<div>
<label for="message">Message :</label>
<textarea id="message" name="user_message"></textarea>
</div>
<div class="button">
<button type="submit">Envoyer votre message</button>
</div>
</form>
and I am looking for a solution after submitted this form, to make show a message with username, email and user's message.
something like;
"hi {username}, thank you for your message. we'll contact you by your {email} after reviewed your message"
I would like to know how I can make a new php page to show these details.

Answer 1

You would show the message on the page that processes your form request.
So if you form goes to processForm.php then when processForm.php is done processing the form it can then return whatever HTML you want it with access to the form values passed to it.
This is not really ideal and is generally handled via the page JS/HTML but if you have specific limits that require this then that is how you do it.
As for a specific example there are many on google for "php form processing"