Describe the flow of an HTTP request from the browser to a PHP application.

When a browser sends an HTTP request to a PHP application, the following flow occurs:

1. DNS resolution: The browser converts the domain name into an IP address of the server.
2. Establishing TCP connection: The browser establishes a connection with the server via IP and port (usually 80 or 443).
3. Sending HTTP request: The browser constructs and sends an HTTP request (GET, POST, etc.) to the server.
4. Web server: The request is received by a web server (e.g., Apache, Nginx) configured to handle PHP.
5. PHP processing: The web server passes the request to the PHP interpreter (via module or FastCGI).
6. Script execution: The PHP script executes, accesses databases and files, and generates a response.
7. Forming HTTP response: The result of the PHP execution is returned to the web server.
8. Sending response: The web server sends the HTTP response back to the browser.
9. Display: The browser receives the response and displays the page to the user.

Thus, the PHP application functions as server-side logic processing requests, while the web server acts as an intermediary between the client and PHP.