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. You can use the output buffering functions to delay the
script output until you have decided whether or not to set any cookies or
send any headers.
Any cookies sent to you from the client will automatically be turned into a
PHP variable just like GET and POST method data, depending on the
register_globals and variables_order
configuration variables. If you wish to assign multiple values to a single
cookie, just add [] to the cookie name.
In PHP 4.1.0 and later, the $_COOKIE auto-global
array will always be set with any cookies sent from the client.
$HTTP_COOKIE_VARS is also set in earlier versions of PHP
when the track_vars configuration variable is set.
For more details, including notes on browser bugs, see the
setcookie() function.
HTTP authentication with PHP
