Cookies are a useful way to save information, for example a user preference or login session locally on the client's machine. PHP makes creating and accessing cookies very easy. To create a cookie called myCookie with the value hello,world, simply add the following line of PHP code:

$expireTime = 60 * 60 * 24 + time();  // 1 day
setcookie("myCookie", "hello,world", $expireTime);

This data will then be available the next time the user loads that particular page. To access the cookie at a later date, use the global $_COOKIE variable:

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if ($_COOKIE["myCookie"] == "hello,world") {
	// some code here
} else {
	// other code here
}

It is also useful to check and see if a user has the cookie saved at all before trying to query it. To do this, use the isset function to test whether or not the variable is defined:

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if (isset($_COOKIE["myCookie"])) {
	// the cookie exists already, use it
} else {
	// the cookie doesn't exist, create it
	setcookie("myCookie", "hello,world", $expireTime);
}