Which function is used to start a session in PHP?

The function that is utilized to start a session in PHP is session_start(). This function is crucial for session management in PHP applications. When invoked, it initializes session data and allows the server to track session variables across subsequent page requests.

The call to session_start() must be made before any output is sent to the browser, which is essential for proper functioning as it sends HTTP headers to establish a session. Once the session is started, PHP will either create a new session ID or resume an existing session using the ID stored in a cookie or passed in the URL.

In this context, other options do not represent valid PHP functions for session management, as they either do not exist or are not defined in the PHP language. Understanding the significance of proper session management and the correct use of session_start() is vital for maintaining user state and data integrity throughout an application.