Populate multiple dropdownlists from sql and previous selected value

Question

I have code in php to query database and populate records in a dropdown list which a user will pick. I also have javascript which populates the second dropdown list based on the selection of the first box.

How do I tie these two together so user selects value "x" from dropdown list, and the php will query the database "WHERE.... = SselectedValue"

Are there any examples online? I can't seem to find any.

Answer 1

Write an ajax/phpquery call to second dropdown on change method of first dropdown. Eg-

$("#firstDdwn").on('change',function(){
   var val=$(this).val();
   //php will query the database "WHERE.... = val"
  //on success of data received from query, populate second dropdown

})

Ajax code is supposed to look something like this-

$.ajax(
{
      url:"your_controller_URL",
      data: val
      success:function(result){
      //populate 2nd dropdown with result
    },
    error:function(){
      alert("No data received");
     }
});

Link for brief info on jquery ajax --- http://www.w3schools.com/jquery/ajax_ajax.asp