does your query give any results?
after this line:
$sqlquery = "SELECT * FROM properties WHERE country = '$country' AND ((price>= $GET[minval]) AND (price <= $GET[maxval]))";
add:
echo $sqlquery."<br>";
re-run script, check if the query is valid (I think you may have problems encapsulating array values like this ... instead of:
$bla = "bla bla $GET[minval] bla";
you should do:
$bla = "bla bla ".$GET['minval']." bla";
) - then, if you have the possibility, paste it into the mysql shell and look if any results are given. If not, the query is the problem.