How to parse input parameters in a search query

Hi

In my custom WP theme a user is making a query which is being processed by a custom theme in functions.php.

Now, a query of this type is passed--
http://dimitri.clientdemos.pw/?post_type=property&search_keyword=1457+Golf+Course+Dr&submit=Search&price-min=&price-max=&city=&state=&zip=&beds=&baths=&sqft=&status=

I just want to obtain the value for "Search Keyword" from the above query? How do I do that? You can see the form here--> http://dimitri.clientdemos.pw/

Thanks,
Arvind.