//your jquery code will be like this:
$.ajax({
      type: 'POST',
      url: $url,
      data: new FormData(this),
      dataType: 'json',
      contentType: false,
      processData:false,//this is a must
      success: function(response){ 
              $('your_selector').html(response);
      }
});

//php code will be like this
echo '
some html code
';
die();