Search form not working properly

My Search form seems to be having some problems. Whenever I search for some text in my posts through the main page or any other page, it’s fine. However, whenever I search for something through one of my static pages, it keeps the static url and adds in the search part at the end…
So if I search for “Test”, it goes:
… /profile.php?s=Test&submit=Go
instead of…
…/?s=Test&submit=Go
I’m sure it has to do with the “Action” part of the form, which should be set to something. The only thing is what should it be changed to. I currently have it at action="<?php echo $PHP_SELF; ?>".
I really have no clue how to fix this.