I’ve been using a commercial WordPress plugin to manage customer testimonials for one of my products. One of the features of the plugin is a tag cloud. The cloud is generated from tags for each testimonial. I’ve used the tags to produce industry specific archives of customer testimonials, which is great for SEO purposes. However, in some cases I’ve created multiple testimonials for the same customer, allowing me to use a short extract or a sentence or two on a landing page rather than having to use the entire testimonial. This resulted in duplicate testimonials from the same customer appearing in the testimonial tag archives. I needed to find a way from stopping this. Here’s how I solved the problem.

First, I added a custom meta field to each duplicate testimonial that I didn’t want to appear in the tag archive. That looks like this:

Defining a Custom Meta Field

Given that the testimonials are custom post types I could filter the testimonials from the tag archives by testing for the existence of the new meta field (in this case I called it testimonial-widget-hide-on-tag-archive). The actual value you assign to the new meta field doesn’t matter. We just want the field to be present for the testimonials we do not want to display on the tag archives. To do that I needed to add an action to the pre_get_posts event and add a filter for the new meta key. Here’s the code I added to my functions.php file:

function modify_testimonial_tag_archive_query( $query ) 
{
	if (is_tag() && $query->is_main_query()) 
	{
		$meta_query[] = array(
                    'key'=>'testimonial-widget-hide-on-tag-archive',
                    'compare'=>'NOT EXISTS',
                );	
		$query->set('meta_query',$meta_query);
  }
}
add_action( "pre_get_posts", "modify_testimonial_tag_archive_query" );

Some key things to note here are the use of is_tag() to check that the query is tag based. Then the use of the $query->is_main_query() call to make sure the filter is used for the main query only (the one that works out what posts to display). The $meta_query array is used to put in the key for the new meta field for the posts we created above, and then we’re using the NOT EXISTS comparison. The result of all this is that only posts that DO NOT have the meta value testimonial-widget-hide-on-tag-archive will be displayed on tag based archives.

I’ve been using PHP in a lot of WordPress posts and pages recently. Usually I just make use of the Exec-PHP plugin. This allows you to put PHP in any page or post using the usual <?php opening and ?> closing tags.  It’s a little clunky for a few reasons, firstly if you edit the page or post in the WordPress Visual editor it messes up the code. You work-around that using the Disable Visual Editor WYSIWYG plugin. A second reason not to do it this way is that editing PHP in the WordPress is horrid. I’d much prefer editing in my IDE of choice where I get nice syntax highlighting and can format the code nicely.

However, there’s a big reason not to include complex PHP directly in your pages or posts. That’s because the PHP is included in the database record for the page or post. Never a great idea from a security point of view. It turns out if you have a need for a complex PHP driven page there’s an easier way. Take the case where we want to create a PHP driven page called “My PHP Page”.

• In your child theme folder (you are using a child theme I hope) create a copy of your page.php file and call it page-my-php-page.php.
• Create a new page in WordPress and call it “My PHP Page”.

Now when WordPress renders the new page called “My PHP Page” and it finds the page-my-php-page.php file in the theme directory it will use that file to generate the page content.

I have found this approach particularly useful if you are building a simple CRUD system in WordPress. I’ve created a series of files called (for example) page-add-record.php, page-delete-record.php, page-edit-record.php, page-view-records.php. Each file contains the code required to add/edit/delete/display the database records I am interested in. Then I just need to create corresponding pages in WordPress with the names “Add Record”, “Edit Record”, “Delete Record”, and “Display Records”.

I’m building a catalog site in WordPress for one of my collections. The catalog currently exists in a large Excel spreadsheet and I’ve been usng it to create a CSV file that can be imported using the WP CSV plugin. This greatly speeds up the creation of the content for the catalog. My plan is that each item in my catalog is a post and the CSV file contains all of the information for each post. One of the imported values in the CSV file includes is the post date. I imported each item with an identical post date without giving it too much thought. This is because the catalog site isn’t going to actually display any post dates. Anyway, it turns out that this was a bad idea because the Next Post and Previous Post links in the single.php template will not bring up any of the posts with the same post date. A bit of digging about and I’ve worked out why.

My single.php theme file contains calls to previous_post_link() and next_post_link() which are supposed to render the next/previous links. I drilled down into these functions which can be found in the /wp-includes/link-template.php file. Both functions call the function get_adjecent_post(). Looking at that a bit closer it includes a bunch of SQL criteria code (for selecting posts from the same taxonomy for example) and, as you’d expect it creates a date criteria clause. That bit of php looks like this:

$adjacent = $previous ? 'previous' : 'next';
 $op = $previous ? '<' : '>';
 $order = $previous ? 'DESC' : 'ASC';

Those little ‘<' and '>‘ symbols give the answer why my imported posts with identical post dates don’t display in the next/previous post links. The date criteria to select the next/previous post is “greater than” or “less than” and obviously if the post dates are identical they are NOT greater than or less than. So, the solution is to NOT import posts with identical post dates. Unfortunately I’d already done this so I opened up the wp_posts table in MySQL workbench and edited the post date of each post I’d imported. Next time I do a bulk import I’ll make sure to increment the post date column values in the CSV BEFORE I do the import.

By default WordPress category archives are sorted by date.  This is fine when you’re publishing a blog but if you’re using WP for other reasons you might want to adjust the way the archives are sorted.  This is done rather easily by creating a new filter in your functions.php file like this:

//filter to alphabetically sort category archives
add_filter('posts_orderby','sort_category_archive_alphabetically');

And then creating a new sort function like this:

function sort_category_archive_alphabetically($orderby )
{
 if (is_category())
 {
 return "post_title ASC";
 }
 return $orderby;
}

In this example I’m alphabetically sorting all categories.  You could restrict it to a specific category by changing the is_category() call to include a category ID (is_category(8)) or by including a category name (is_category(‘Your Category Name’)).

I’m doing a simple sort by post_title here but more complex sorts are possible.  For example, the WordPress API gives a more complex example that explains how to do a LEFT JOIN in the SQL to select posts and sort by values in tables other than the WP_POSTS table.

I’m building a numismatic reference website in WordPress for the Perth Numismatic Society that is eventually going to list several thousand items along with images. The images will be presented as thumbnails which can be clicked on to show larger images using the Responsive Lightbox plugin. The client wanted a default caption under each image instructing users to click on the image to view a larger one. I honestly thought adding a default image caption would be easy but it turns out it isn’t. Nothing I Googled up actually worked including this example in the WordPress Codex or this plugin. So I actually had to use the old grey matter and work it out myself.

So I had a poke around the and ended up in the /wp-admin/includes/media.php file and found this function and filter:

function image_add_caption( $html, $id, $caption, $title, $align, $url, $size, $alt = '' )
{
//function code removed
}
add_filter( 'image_send_to_editor', 'image_add_caption', 20, 8 );

Ahah, simple. Remove the existing image_add_caption filter and replace it with my own. So, I’ve grabbed that code and added it and a couple of other things to my child theme functions.php file as:

remove_filter( 'image_send_to_editor', 'image_add_caption');
add_filter( 'image_send_to_editor', 'add_default_caption', 100, 8);
function add_default_caption( $html, $id, $caption, $title, $align, $url, $size, $alt = '' ) {

	/**
	 * Filter whether to disable captions.
	 *
	 * Prevents image captions from being appended to image HTML when inserted into the editor.
	 *
	 * @since 2.6.0
	 *
	 * @param bool $bool Whether to disable appending captions. Returning true to the filter
	 *                   will disable captions. Default empty string.
	 */
        if (substr($html,0,strlen('([0-9]+)/', $html, $matches ) )
		return $html;

	$width = $matches[1];

	$caption = str_replace( array("rn", "r"), "n", $caption);
	$caption = preg_replace_callback( '/<[a-zA-Z0-9]+(?: [^<>]+>)*/', '_cleanup_image_add_caption', $caption );
	// convert any remaining line breaks to <br>
	$caption = preg_replace( '/[ nt]*n[ t]*/', '<br />', $caption );

	$html = preg_replace( '/(class=["'][^'"]*)align(none|left|right|center)s?/', '$1', $html );
	if ( empty($align) )
		$align = 'none';

	$shcode = '' . $html . ' ' . $caption . '';

	/**
	 * Filter the image HTML markup including the caption shortcode.
	 *
	 * @since 2.6.0
	 *
	 * @param string $shcode The image HTML markup with caption shortcode.
	 * @param string $html   The image HTML markup.
	 */
	return apply_filters( 'image_add_caption_shortcode', $shcode, $html );
}

You can see I start by removing the existing image_add_caption filter but it turns out this is an utter waste of time because the filter executes even though I’ve removed it. So I’ve got around this by declaring the new filter with a lower priority than the existing one (so it happens AFTER) the existing filter. And then checked the $html to see if it starts with the caption shortcode. That’s this line:

if (substr($html,0,strlen('[caption'))=='[caption')
 return $html;

So, if a caption has already been applied we just exit from our new filter.  However, if there’s no caption we can now apply our default caption like this:

if (empty($caption))
 $caption="Click Image to Enlarge";