Thanks for helping ;-)
What I whant to do is to add an extra option to the spider.php crawler : this option will contain a string like "SID=202ab26bc69" and will be sent as a cookie by phpdig while it is browsing a site.
for instance :
spider.php
http://www.mysite.com "SID=jqgjgqsg"
will send the header
Cookie: SID=jqgjgqsg
for every sent to
www.mysite.com
Any idea or patch to use ?