Which function in PHP is used to create a cookie?

The function used to create a cookie in PHP is setcookie(). This function allows you to send a cookie to the user's browser, enabling you to store data between sessions. When you call setcookie(), you can specify parameters such as the cookie name, value, expiration time, path, domain, and other attributes.

Using setcookie() correctly involves understanding how cookies work in HTTP and web applications. When you send a cookie, it is included in the HTTP response headers, and upon the next request from the same client, the browser includes the cookie in the request headers, making the information available to the server.

The naming convention of the function is case-sensitive. PHP recognizes functions exactly as they are declared, which is why it's essential to note that 'setcookie()' is the proper way to call this function in code. Other options provided do not exist in PHP, so they cannot be used to create a cookie.