#! code

Here are some of the regular expressions that I frequently use.

Find a blank line

^$

Spaces

[ \t]+

You can use this to break a text string apart into words.

Date

\d{1,2}(\-|\/|\.)\d{1,2}\1\d{4}

This will match anything in the format mm/dd/yyyy, or even dd/mm/yyyy.

PHP keeps certain variables to do with server and networking in an associative array called SERVER. To find out the remote address of a user you can use the array identifier REMOTE_ADDR. This is used in the following manner.

$ipaddress = $_SERVER['REMOTE_ADDR'];

This IP address can be passed into the gethostbyaddr() function to find out host name associated with the specified IP address.