Adding post template names to post_class()

For my currently work-in-progress-theme, I want to display posts with post templates different in the blog view. For that, I add the name of the post template to the post_class() output via the post_class filter. This post shows you how to get this working.

Function for returning the post template slug

Because I need the name of the post templates in various places of the theme, we write a function for returning the post template name first:

if ( ! function_exists( 'photographia_get_post_type_template' ) ) {
	/**
	 * Returns the post type template slug 
	 * without templates/ dir and .php ending.
	 *
	 * @return string
	 */
	function photographia_get_post_type_template() {
		$template_slug = get_page_template_slug();
		if ( '' !== $template_slug ) {
			/**
			 * Remove »templates/« from slug.
			 */
			$template_slug = str_replace( 'templates/', '', $template_slug );

			/**
			 * Remove .php file ending.
			 */
			$post_type_template = str_replace( '.php', '', $template_slug );

			return $post_type_template;
		} else {
			return '';
		}
	}
}
Code language: PHP (php)

At the first line, we check if the function photographia_get_post_type_template() was previously defined by a child theme (or plugin). Inside the function, we determine the current’s post template slug with get_page_template_slug(). If the post has no template, the function call returns an empty string. If the result is not empty, the theme’s template slugs look like that: templates/name-of-template.php. We do not need the templates/ part and the .php ending — let us remove them with two str_replace() calls and return the $post_type.

If the post has no template, we return an empty string.

Function for adding the class

Now the function, which filters the post_class:

/**
 * Add classes to post_class()
 *
 * @param array $classes array with post classes.
 *
 * @return array
 */
function photographia_filter_post_classes( $classes ) {
	/**
	 * Get the post type template name.
	 * Empty string if no template is used.
	 */
	$post_type_template = photographia_get_post_type_template();

	/**
	 * Add post template class if post has a template
	 */
	if ( '' !== $post_type_template ) {
		$classes[] .= "-$post_type_template-template";
	}

	return $classes;
}

add_filter( 'post_class', 'photographia_filter_post_classes' );
Code language: PHP (php)

We get the string of the post template name — or an empty string if no template is used — by calling our photographia_get_post_type_template() function. If the function does not return an empty string, we add a new array value to $classes and return the classes array.

Now if a post has a template, calling the post_class() function in the loop returns a class with the pattern -templatename-template.