Ajax not completing

var php_params = "job=SearchForm&task=PartialForm&tablename=Customer&uniq_field_value="+cust_name ; 
      var fields_to_BU = ['cust_name', 'cust_desig_2char', 'cust_desig_3char', 'region'] ;
      var customer_id ;
      $('#debug').html(php_params) ;
      
      $.ajax({
      url: '/cmdb/PHP/do_FormSearch_query.php',
      method:     "GET" ,
      cache:      false ,
      data:       encodeURIComponent(php_params)  ,
      dataType:   'JSON'
      }).done(function(data) 
      {
        alert("HERE THREE!");
        customer_id = data.customer_id ;
        $('input [name=cust_desig_2char]').val(data.cust_desig_2char) ;
        $('input [name=cust_desig_3char]').val(data.cust_desig_3char) ;
        $('input [name=region]').val(data.region) ;
        
        $('#RtMgn_Customer').val(customer_id) ;
        
         blah blah blah;
        
        
      })  ;  // EO AJAX .done function()

case "PartialForm":
        
        $uniq_field_value = htmlspecialchars($_GET['uniq_field_value']) ; 
        $tablename = htmlspecialchars($_GET['tablename']) ;
        
        switch($tablename)
        {
        case 'Customer':
          
          do_mysql_multi("SELECT * FROM Customer WHERE `cust_name`= '".$uniq_field_value."' ;", 1, $result_vector1, $result_vector2) ;
          
          echo json_encode($result_vector1['values'][1]) ;
          
          break ;

{"customer_id":"76","cust_name":"QATAR AIRWAYS","cust_desig_2char":"QR","cust_desig_3char":"QTR","region":"Middle East","note_id":"75750"}