PHP transparently supports HTTP cookies. Cookies are a mechanism for storing data in the remote browser and thus tracking or identifying return users. You can set cookies using the setcookie() function. Cookies are part of the HTTP header, so setcookie() must be called before any output is sent to the browser. This is the same limitation that header() has.
Any cookies sent to you from the client will automatically be turned into a PHP variable just like GET and POST method data. If you wish to assign multiple values to a single cookie, just add  to the cookie name. For more details see the setcookie() function.