Not getting output on template after Ajax request

I’m really stumped and hoping someone can help.

Basicly what I’m trying to do is get the content of a div changed depending on which button you press.

I have 4 buttons and 1 div for the dynamic content. See my testpage here: https://www.pixelein.nl/testpagina/
At the moment you see all the possible content in the dynamic content section. The dynamic content should appear below this default content (placed for comparison).

I got it far enough that the Ajax response is up and running. If you click on button three, you see the Ajax response showing the correct dynamic content.
However, I cannot figure out why the dynamic content isn’t loading into the div.

My jQuery code in footer.php:

jQuery('.but').click(function(){

		if(jQuery(this).hasClass('one')) {
			var data = {
			  action: 'view_portfolio',
			  galleryID: 1
			};

			jQuery.post(ajaxurl, data, function(response) {
				//alert('Got this from the server: ' + response);
			});
		} else if(jQuery(this).hasClass('two')) {
			var data = {
			  action: 'view_portfolio',
			  galleryID: 2
			};

			jQuery.post(ajaxurl, data, function(response) {
				//alert('Got this from the server: ' + response);
			});
		} else if(jQuery(this).hasClass('tre')) {
			var data = {
			  action: 'view_portfolio',
			  galleryID: 3
			};

			jQuery.post(ajaxurl, data, function(response) {
				alert('Got this from the server: ' + response);
			});
		} else {
			var data = {
			  action: 'view_portfolio',
			  galleryID: 4
			};

			jQuery.post(ajaxurl, data, function(response) {
				//alert('Got this from the server: ' + response);
			});
		}
		return false;
  	});

My code in my themes functions.php:

add_action( 'wp_ajax_view_portfolio', 'view_portfolio' );
add_action( 'wp_ajax_nopriv_view_portfolio', 'view_portfolio' );
function view_portfolio(){

  // look up for the path
  if ( !defined('ABSPATH') )
	  require_once( dirname(__FILE__) . '/../ngg-config.php');

  global $wpdb;

  $ngg_options = get_option ('ngg_options');
  $siteurl	 = site_url();

  // get the gallery id
  $galleryID = intval( $_POST['galleryID'] );
  if ($galleryID == null) {
	  $galleryID = 1;
  } else {
	  $galleryID = intval( $_POST['galleryID'] );
  }

  // get the pictures
  if ($galleryID == 0) {
	  $thepictures = $wpdb->get_results("SELECT t.*, tt.* FROM $wpdb->nggallery AS t INNER JOIN $wpdb->nggpictures AS tt ON t.gid = tt.galleryid WHERE tt.exclude != 1 ORDER BY tt.{$ngg_options['galSort']} {$ngg_options['galSortDir']} ");
  } else {
	  $thepictures = $wpdb->get_results("SELECT t.*, tt.* FROM $wpdb->nggallery AS t INNER JOIN $wpdb->nggpictures AS tt ON t.gid = tt.galleryid WHERE t.gid = '$galleryID' AND tt.exclude != 1 ORDER BY tt.{$ngg_options['galSort']} {$ngg_options['galSortDir']} ");
  }

  if (is_array ($thepictures)){
	  foreach ($thepictures as $picture) {
		  echo $picture->filename;
		  echo ' - ';
		  echo $siteurl."/".$picture->path."/".$picture->filename;
		  echo '<br/>';
	  }
  }
  echo $thepictures;

  //die();
  //exit;

}

on the template page:

<div id="view_portfolio">
                  <div class="but one">knop 1</div>
                  <div class="but two">knop 2</div>
                  <div class="but tre">knop 3</div>
                  <div class="but qua">knop 4</div>
                </div>

                <div id="fotos">
                	<?php view_portfolio(); ?>
                    <br />
                    ---------
                    <br />
                    <br />
                    <?php view_portfolio($thepictures) ?>
                </div>