Custom Post Rewrites for Josh

cpt-example.php

<?php

/*
Plugin Name:  Example Custom Post Types
Plugin URI:   https://deadhandmedia.com/
Description:  Adds custom post types and taxonomies.
Version:      1.0.0
Author:       Tyler Smith
Author URI:   https://deadhandmedia.com/
License:      GPL2
License URI:  https://www.gnu.org/licenses/gpl-2.0.html
Text Domain:  example-text-domain
Domain Path:  /languages
*/

require_once ( dirname( __FILE__ ) . '/cpt-label-helper.php' );

class CPT_Example {

	private $text_domain = 'example-text-domain';

	public function __construct() {
		add_action( 'init', [ $this, 'register_post_types' ] );
		add_action( 'init', [ $this, 'register_taxonomies' ] );
		add_action( 'init', [ $this, 'add_rewrite_rules' ] );
		add_filter( 'term_link', [ $this, 'update_term_link' ], 10, 3 );
		add_filter( 'post_type_link', [ $this, 'update_post_type_link' ], 10, 2 );
		add_filter( 'template_redirect', [ $this, 'redirect_on_wrong_url' ] );

		register_activation_hook( __FILE__,  [ $this, 'activate' ] );
		register_deactivation_hook( __FILE__, 'flush_rewrite_rules' );
	}

	/**
	 * Add custom post types and taxomonies then flush permalinks.
	 *
	 * @link https://developer.wordpress.org/reference/functions/flush_rewrite_rules/#comment-597
	 */
	public function activate() {
		// Register rewrite rules before init hook so WordPress has access to 
		// the post type and taxonomy slugs.
		$this->register_post_types();
		$this->register_taxonomies();

		// Flush the rewrite rules so these types are included.
		flush_rewrite_rules();
	}

	/**
	 * Register custom post types.
	 * 
	 * @link https://codex.wordpress.org/Function_Reference/register_post_type
	 * @link https://developer.wordpress.org/resource/dashicons/
	 */
	public function register_post_types() {
		// Register Careers
		$args = [
			'labels'             => CPT_Label_Helper::post_type('Career', 'Careers', $this->text_domain),
			'public'             => true,
			'publicly_queryable' => true,
			'show_ui'            => true,
			'show_in_menu'       => true,
			'query_var'          => true,
			'rewrite'            => array( 'slug' => 'careers' ),
			'capability_type'    => 'post',
			'has_archive'        => false,
			'hierarchical'       => false,
			'menu_position'      => null,
			'menu_icon'          => 'dashicons-universal-access-alt',
			'supports'           => array( 'title', 'editor', 'thumbnail')
		];

		register_post_type( 'career', $args );
	}

	/**
	 * Register custom taxonomies.
	 * 
	 * @link https://codex.wordpress.org/Function_Reference/register_taxonomy
	 */
	public function register_taxonomies() {
		// Career Type
		$args = [
			'hierarchical'          => true,
			'labels'                => CPT_Label_Helper::hierarchical_taxonomy('Career Type', 'Career Types', $this->text_domain),
			'show_ui'               => true,
			'show_admin_column'     => true,
			'update_count_callback' => '_update_post_term_count',
			'query_var'             => true,
			'rewrite'               => [ 
				'slug' => 'career-type',
			],
		];
		register_taxonomy( 'career-type', array( 'career' ), $args );
	}

	/**
	 * Adds rewrite rules for WordPress to match against and set the query 
	 * variables.
	 * 
	 * @link https://developer.wordpress.org/reference/functions/add_rewrite_rule/
	 */
	public function add_rewrite_rules() {

		// For single career page. Example:
		// https://jobs.com/careers/tech/wordpress-developer/
		add_rewrite_rule(
			'careers/([^/]+)/([^/]*)?/?$',
			'index.php?post_type=career&career-type=$matches[1]&name=$matches[2]',
			'top'
		);

		// For career type taxonomy page. Example: 
		// https://jobs.com/careers/tech/
		add_rewrite_rule(
			'careers/([^/]+)?/?$',
			'index.php?post_type=career&career-type=$matches[1]',
			'top'
		);
	}

	/**
	 * Updates the post link. Even though we have the rewrite rules above,
	 * WordPress only uses that to create a query and delivery the posts 
	 * matching that query. In order to make sure that system permalinks
	 * match the desired URL, we must explicitly set in in WordPress.
	 *
	 * There is some added complexity to ensure that WordPress still allows
	 * the user to edit the post slug, which is why there is specific logic
	 * for that below. I've included links for further reading on the reasoning
	 * behind this code.
	 * 
	 * @link https://kellenmace.com/edit-slug-button-missing-in-wordpress/
	 * @link https://wordpress.stackexchange.com/questions/275687/how-to-retain-the-ability-to-modify-the-post-slug-after-applying-a-post-type-lin
	 * @link https://codex.wordpress.org/Plugin_API/Filter_Reference/post_type_link
	 */
	public function update_post_type_link( $url, $post ) {

		if ( false !==  strpos( $url, "%career%" ) ) {
			$slug = '%career%';
		} elseif ( $post->post_name ) {
			$slug = $post->post_name;
		} else {
			$slug = sanitize_title( $post->post_title );
		}

		$term = get_the_terms( $post->ID, 'career-type' );

		// Set fallback if no category is selected.
		$term_slug = $term[0]->slug ?? 'other';

		return user_trailingslashit( home_url( "careers/{$term_slug}/{$slug}" ) );
	}

	/**
	 * Updates the taxonomy link. Like posts, even though we have new rewrite
	 * rules added, WordPress must be explicitly told what we want the the 
	 * term permalink to be.
	 * 
	 * @link https://codex.wordpress.org/Plugin_API/Filter_Reference/post_type_link
	 */
	public function update_term_link( $url, $term, $taxonomy ) {
		return user_trailingslashit( home_url( "careers/{$term->slug}" ) );
	}

	/**
	 * In the update_post_type_link() method, we tell WordPress what the post
	 * link should be. However, the WordPress query is only matching by a 
	 * regex pattern. This means that any characters in the preappended 
	 * taxonomy could match and pull up the page, because the query is 
	 * matching by the slug. This could create endless duplicate pages 
	 * with similar URLs, which has bad implications for SEO.
	 *
	 * To mitigate this, we will check if the currently url matches what we
	 * expect, and if it does not we'll redirect the user to the correct URL.
	 *
	 * @link https://codex.wordpress.org/Plugin_API/Action_Reference/template_redirect
	 */
	public function redirect_on_wrong_url() {
		if ( 'career' != get_post_type() ) return;
		if ( is_archive() ) return;
		global $wp;
		$permalink = user_trailingslashit( get_the_permalink() );
		$current_page = user_trailingslashit( home_url(  $wp->request ) );
		if( $current_page != $permalink ){
			wp_redirect( $permalink );
			die();
		}
	}

}

new CPT_Example;

cpt-label-helper.php

<?php 

class CPT_Label_Helper {
	public static function post_type ($singular, $plural, $textdomain = '') {
		$labels = array(
			'name'               => __( $plural, $textdomain ),
			'singular_name'      => __( $singular, $textdomain ),
			'menu_name'          => __( $plural, $textdomain ),
			'name_admin_bar'     => __( $singular, $textdomain ),
			'add_new'            => __( 'Add New', $textdomain ),
			'add_new_item'       => __( 'Add New ' . $singular, $textdomain ),
			'new_item'           => __( 'New ' . $singular, $textdomain ),
			'edit_item'          => __( 'Edit ' . $singular, $textdomain ),
			'view_item'          => __( 'View ' . $singular, $textdomain ),
			'all_items'          => __( 'All ' . $plural, $textdomain ),
			'search_items'       => __( 'Search ' . $plural, $textdomain ),
			'parent_item_colon'  => __( 'Parent ' . $plural . ':', $textdomain ),
			'not_found'          => __( 'No ' . strtolower($plural) .  ' found.', $textdomain ),
			'not_found_in_trash' => __( 'No ' . strtolower($plural) .  ' found in Trash.', $textdomain )
		);

		return $labels;
	}

	public static function hierarchical_taxonomy($singular, $plural, $textdomain = '') {
		$labels = array(
			'name'                       => __( $plural, $textdomain ),
			'singular_name'              => __( $singular, $textdomain ),
			'search_items'               => __( 'Search ' . $plural, $textdomain ),
			'popular_items'              => __( 'Popular ' . $plural, $textdomain ),
			'all_items'                  => __( 'All ' . $plural, $textdomain ),
			'parent_item'                => null,
			'parent_item_colon'          => null,
			'edit_item'                  => __( 'Edit ' . $singular, $textdomain ),
			'update_item'                => __( 'Update ' . $singular, $textdomain ),
			'add_new_item'               => __( 'Add New ' . $singular, $textdomain ),
			'new_item_name'              => __( 'New ' . $singular . ' Name', $textdomain ),
			'menu_name'                  => __( $plural, $textdomain ),
		);
		
		return $labels;
	}

	public static function non_hierarchical_taxonomy($singular, $plural, $textdomain = '') {
		$labels = array(
			'name'                       => __( $plural, $textdomain ),
			'singular_name'              => __( $singular, $textdomain ),
			'search_items'               => __( 'Search ' . $plural, $textdomain ),
			'popular_items'              => __( 'Popular ' . $plural, $textdomain ),
			'all_items'                  => __( 'All ' . $plural, $textdomain ),
			'parent_item'                => null,
			'parent_item_colon'          => null,
			'edit_item'                  => __( 'Edit ' . $singular, $textdomain ),
			'update_item'                => __( 'Update ' . $singular, $textdomain ),
			'add_new_item'               => __( 'Add New ' . $singular, $textdomain ),
			'new_item_name'              => __( 'New ' . $singular . ' Name', $textdomain ),
			'separate_items_with_commas' => __( 'Separate ' . strtolower($plural) . ' with commas', $textdomain ),
			'add_or_remove_items'        => __( 'Add or remove ' . strtolower($plural), $textdomain ),
			'choose_from_most_used'      => __( 'Choose from the most used ' . strtolower($plural), $textdomain ),
			'not_found'                  => __( 'No ' . strtolower($plural) .' found.', $textdomain ),
			'menu_name'                  => __( $plural, $textdomain ),
		);

		return $labels;
	}
}