Ajax not completing

This used to work, I lost some code, thank you Windows, and now it doesn't.

The PHP does its thing and returns, but nothing happens on the return to JavaScript.  No "HERE THREE!"!

The JS AJAX code:

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()

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The PHP:

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 ;

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What PHP returns (sample):

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

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