What is the purpose of setting a cookie in PHP and how does it affect website functionality?

Setting a cookie in PHP allows you to store data on the user's browser, which can be accessed and used across different pages on your website. This can be useful for maintaining user sessions, remembering user preferences, or tracking user behavior. To set a cookie in PHP, you can use the setcookie() function.

// Set a cookie named "user_id" with a value of 123
setcookie("user_id", "123", time() + 3600, "/");