Unable to save data in Database through ajax in CakePhp after passing my own array variable in save function?

This is my view ctp page ....

<h1>Add Post</h1>
<?php echo $this->form->create(null,array('url'=>array('controller'=>'posts','action'=>'ajaxAdd'),'id'=>'saveForm'));
echo $this->form->input('ajaxtitle');
echo $this->form->input('ajaxbody',array('rows'=>'3'));
echo $this->form->end('Save Post');
?>

<script>
    $(document).ready(function(){
    $("#saveForm").submit(function(){       
        var formData = $(this).serialize();
        var formUrl = $(this).attr('action');
        $.ajax({

            type:'POST',
            url:formUrl,
            data:formData,
            success: function(data,textStatus,xhr){
                alert(data);                                       
                }

        });
        return false;
    });
});
</script>

This is my PostsController function

class PostsController extends AppController
{

        public $name = 'Posts';
        public $helpers = array('Html', 'Form', 'Session');
        public $components  = array('RequestHandler');
public function ajaxAdd()
    {
        $this->autoRender=false;
          if($this->RequestHandler->isAjax()){
             Configure::write('debug', 0);
          }
            if(!empty($this->data)){
                $inputData = array();
                $inputData['Post']['title'] = $this->data['Post']['ajaxtitle'];
                $inputData['Post']['body'] = $this->data['Post']['ajaxbody'];
                $data = $this->Post->findByTitle($inputData['Post']['title']);
                $this->Post->create();
               if(empty($data))
               {                   
                  if($this->Post->save($inputData))
                      return "success"; 
                }else
                {
                 return "error";
               }
            }
        }
}

With array as $inputData in save , whenever i click over the submit button nothing is being saved in the database ,,

But when i pass $this->data in save function, columns like id,created and modified are filled but the title and body column are left blank.

My posts databse contains columns id,title,body,created,modified