Under certain circumstances, some scripts will not allow posting using query string only, eg. you may need to actually click the Submit button, or need to enter a confirmation code. All of this is to prevent spammers posting remotely.
However, If non of the above apply, you can post remotely using query string.
To do this:
examine the form tags
note the NAME of each form field
take the URL of the form
append ?
then 'form field name' and 'value' combo.
Eg. say url is http://www.isp.com/someform.php
and
field names are LOGIN, PASSWD
then typing the following into the address window of your browser will post the data: http://www.isp.com/someform.php?LOGIN=xxxx&PASSWD=xxxx
You just replace xxxx with the correct values.
http://sabyo.ath.cx
Power to PHP!