IP Check

i have forms set up to add entry's to a database from my site. as well as the form information that will be submitted to the database, for security reasons i would also like to add the submitter's IP to my database. I know how to grab the IP on my form using perl or PHP, but after the form is submitted or i go into another script phrase, the variable is no longer available. How would one take a variable from a PHP or perl script on my page, and use it in the form so that when i click submit...the IP will be carried to the database along with the form data? This is for use in security where its necessary to track the user's IP by adding it to the database, so the person who added the entry will have his or her IP in the database as well in its own field along with the new record. Does it have something to do with the global settings, or is it impossible to add PHP or Perl variables into and html form? Anyone know anything about doing this kinda thing? thanks,
john