Pre-set variables  Before you even get control in your script,
PHP has set a number of variables for you containing information
about the server, the environment, and the request from your
visitor. These are stored in the superglobal arrays for you, and
you can get a fairly complete list of what is available by using
the phpinfo() output.  The most commonly used variables, all of
which are stored in the $_SERVER superglobal, are as follows:
If the user clicked a link to get the current page, this will
contain the URL of the previous page they were at, or it will be
empty if the user entered the URL directly.   The name reported
by the visitor's browser   Any data passed in the URL after the
script name   The name of the current script   Either GET or
POST   Includes everything after the question mark in a GET
request  Note that you need to use HTTP_REFERER and not
HTTP_REFERRER. This is one of the very few misspellings ever to
make it into a web standard, but is now in widespread use and so
too late to ch