jQuery AJAX dataType:“json” can't use it … just use Array instead

Originally I was trying to send a Javascript JSON Object to a PHP page, without success. Using the following test code:

var testobj = {
  "test1":"test1data",
  "test2":"test2data",
  "test3":"test3data"
};
alert(testobj.test1);
$.ajax({
  type: "POST",
  url: "ajaxtest.php",
  dataType: "json",
  data: testobj
})
  .error(function( msg ) {
    alert( "Error: " + msg );
  })
  .success(function( msg ) {
    alert( "Success: " + msg );
  });

Never sends the data, and always returns an error.

Removing the 'dataType' attribute or defining it as anything other than 'json' returns 'success', but still no data is sent.

I can use the exact same Object code as the 'data:' value and it DOES get sent, but not when I use the JSON Object.

So I send an Array, instead:

var testobj = new Array();
testobj = {
  "test1":"test1data",
  "test2":"test2data",
  "test3":"test3data"
};
alert(testobj.test1);
$.ajax({
  type: "POST",
  url: "ajaxtest.php",
  data: testobj
})
  .error(function( msg ) {
    alert( "Error: " + msg );
  })
  .success(function( msg ) {
    alert( "Success: " + msg );
  });

Exactly the same code, except (a) I defined the variable as an Array instead of a JSON Object and (b) I removed the 'dataType' attribute from the .ajax call.

Grab the Array elements on the target page using the $_POST array.

I never much cared for JSON as a method for passing data, anyway, so this doesn't exactly worry me. But I do wonder about the current state of jQuery (v.1.9.1)

Is there something wrong with my JSON construction? What's the deal with sending a JSON Object via jQuery AJAX? And why is there a problem with the 'dataType: "json"' attribute?