Drupal.in Drupal India User Group

hi,

i am trying o call a php file through ajax using following code inside a page in my themes directory:

$(document).ready(function(){
$("#selectionresult").hide();

$("#country").change( function() {
$("#selectionresult").hide();
$("#result").html('Retrieving ...');
$.ajax({
type: "POST",
data: "data=" + $(this).val(),
url: "<?php echo path_to_theme(); ?>/get_states.php",
success: function(msg){
if (msg != ''){
$("#selectionresult").html(msg).show();
$("#result").html('');
}
else{
$("#result").html('No item result');
}
}
});
});
});

The get_states.php file makes use of db_query and other drupal functions. but i keep getting Fatal Error: call to undefined function db_query() error,plz suggest me a way to resolve this issue.

Thanks,
Kul.