User: Hey, I'm working on a PHP project and I need some help with using variables passed through the `header()` function. I have a basic understanding of PHP, but I'm not quite sure how to handle variables passed through this function.
Context: I'm currently working on a web application that requires user authentication. I have a login form where users enter their credentials, and once their credentials are validated, I want to redirect them to a welcome page displaying their username.
Question: How can I pass the user's username through the `header()` function and then retrieve and use it on the welcome page in PHP?
I would appreciate any assistance or guidance on the correct approach to achieve this. Thanks a lot!

User 1: Hey there! Passing variables through the `header()` function in PHP is certainly possible and can be really useful. In the context of your authentication scenario, here's how you can achieve it.
First, after validating the user's credentials, you can set the username as a variable. For example, you can store it in a session variable like this:
Then, use the `header()` function to redirect the user to the welcome page:
On the welcome.php page, make sure to start the session again and retrieve the username from the session variable:
Now, you can use the `$username` variable as per your requirement on the welcome page to personalize the user's experience.
Remember, it's important to call `session_start()` at the beginning of each PHP file where you want to use session variables.
I hope that helps! Let me know if you have any further questions or need more clarification.