[WordPress] WP_Query Readability Improvements For Yourself (And Others)

00-wp-query.php

<?php

// Assume this is defined within the context of a class.
const MAPPING = [
		'employers'       => 'page-past-word.php',
		'biography'       => 'page-biography.php',
		'accomplishments' => 'page-csv.php',
	];

/* Snip the rest of the class for brevity */

public function map_templates() {
  
  $args = [
    'post_type'      => array( 'post', 'page' ),
    'post_status'    => 'publish',
    'orderby'        => 'ID',
    'order'          => 'ASC',
    'posts_per_page' => -1,
  ];
  $template_query = new \WP_Query( $args );
  
	if ( $template_query->have_posts() ) {
		while ( $template_query->have_posts() ) {
			$template_query->the_post();
	
			$template_id = get_post_meta( $post_id, 'third_party_template_id', true );
			if ( '' === $template_id ) {
				continue;
			}

      			// The third-party's template post name can be used to map our custom template.
			$template_info = get_post( $template_id );
			$template_name = $template_info->post_name;

			if ( isset( self::MAPPING[ $template_name ] ) ) {
        
				$template_file = self::MAPPING[ $template_name ];
				update_post_meta( $post_id, '_wp_page_template', $template_file );
			}
		}
	}
}

01-map-page-templates.php

<?php

public function map_page_templates() {

  $posts = $this->load_posts_and_pages();
  if ( $posts->have_posts() ) {
    $this->assign_templates( $posts );
  }
}

02-load-posts-and-pages.php

<?php

private function load_posts_and_pages() {

  $args = [
    'post_type'      => array( 'post', 'page' ),
    'post_status'    => 'publish',
    'orderby'        => 'ID',
    'order'          => 'ASC',
    'posts_per_page' => -1,
  ];
  $posts = new \WP_Query( $args );

  return $posts;
}

03-assign-templates.php

<?php

private function assign_templates( \WP_Query $posts ) {

  while ( $posts->have_posts() ) {
    $posts->the_post();

    $template_id = $this->get_template_id( get_the_ID() );
    if ( '' === $template_id ) {
      continue;
    }

    $template_name = $this->get_template_name( $template_id );
    if ( null === $template_name ) {
      continue;
    }

    $this->assign_template( get_the_ID(), $template_name );
  }
  wp_reset_postdata();
}

04-get-template-id.php

<?php

private function get_template_id( $post_id ) {

  $template_id = get_post_meta( $post_id, 'third_party_template_id', true );
  return $template_id;
}

05-get-template-name.php

<?php

private function get_template_name( $template_id ) {

  $template_info = get_post( $template_id );
  $template_name = $template_info->post_name;

  if ( isset( self::MAPPING[ $template_name ] ) ) {
    return $template_name;
  } else {
    return null;
  }
}

06-assign-template.php

<?php

private function assign_template( $post_id, $template_name ) {

  $template_file = self::MAPPING[ $template_name ];
  update_post_meta( $post_id, '_wp_page_template', $template_file );
}