ajax triple drop down menu

[z99]

in my region table i have 4 fields=>id,oid,cid,name [oid and cid are primary key which refer to ostan and city tables]

in the third drop down menu when region is selected this codes will be executed:

else if($data=='region')
{ //third dropn down menu
echo "<select name='region' >\n";
echo "<option value='0'>====choose region====</option>\n";  
$qth="select id,name from region where oid='$oid' and cid='$val'"; ************HERE**************
$exeqth=mysql_query($qth,$l);
while($res3=mysql_fetch_array($exeqth))
{
echo "<option value=\"$res3[id]\" >$res3[name]</option> \n" ;
}
}//close for if region

as you see i have to check,oid [which refers to countrty table] and cid [which refers to city table],in order to show the region that is really belong to country and the city that the user has been select,there is $val that contains the selection,unfortunately it will save the selection from the first drop down menu,i should deal with $val,because this is the variable that contain the selection,how can save each value from each drop down menu in 3 variables $country,$city,$region,

 

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