class-pager-template.php

<?php

class PageTemplater {

 /**
  * A reference to an instance of this class.
  */
 private static $instance;

 /**
  * The array of templates that this plugin tracks.
  */
 protected $templates;

 /**
  * Returns an instance of this class.
  */
 public static function get_instance() {

   if ( null == self::$instance ) {
     self::$instance = new PageTemplater();
   }

   return self::$instance;

 }

 /**
  * Initializes the plugin by setting filters and administration functions.
  */
 private function __construct() {

   $this->templates = array();


   // Add a filter to the attributes metabox to inject template into the cache.
   if ( version_compare( floatval( get_bloginfo( 'version' ) ), '4.7', '<' ) ) {

     // 4.6 and older
     add_filter(
       'page_attributes_dropdown_pages_args',
       array( $this, 'register_project_templates' )
     );

   } else {

     // Add a filter to the wp 4.7 version attributes metabox
     add_filter(
       'theme_page_templates', array( $this, 'add_new_template' )
     );

   }

   // Add a filter to the save post to inject out template into the page cache
   add_filter(
     'wp_insert_post_data',
     array( $this, 'register_project_templates' )
   );


   // Add a filter to the template include to determine if the page has our
   // template assigned and return it's path
   add_filter(
     'template_include',
     array( $this, 'view_project_template')
   );


   // Add your templates to this array.
   $this->templates = array(
     'template/page-eventos.php' => 'Lista de Eventos',
     'template/page-notificacao.php' => 'Notificação',
     'template/page-minha-conta.php' => 'Minha Conta',
     'template/page-selecionar-ingresso.php' => 'Selecionar Ingresso',
     'template/page-cadastrar.php'  => 'Cadastrar',
     'template/page-conta.php'  => 'Conta',
     'template/page-resumo-compra.php'  => 'Resumo da Compra',
   );

 }

 /**
  * Adds our template to the page dropdown for v4.7+
  *
  */
 public function add_new_template( $posts_templates ) {
   $posts_templates = array_merge( $posts_templates, $this->templates );
   return $posts_templates;
 }

 /**
  * Adds our template to the pages cache in order to trick WordPress
  * into thinking the template file exists where it doens't really exist.
  */
 public function register_project_templates( $atts ) {

   // Create the key used for the themes cache
   $cache_key = 'page_templates-' . md5( get_theme_root() . '/' . get_stylesheet() );

   // Retrieve the cache list.
   // If it doesn't exist, or it's empty prepare an array
   $templates = wp_get_theme()->get_page_templates();
   if ( empty( $templates ) ) {
     $templates = array();
   }

   // New cache, therefore remove the old one
   wp_cache_delete( $cache_key , 'themes');

   // Now add our template to the list of templates by merging our templates
   // with the existing templates array from the cache.
   $templates = array_merge( $templates, $this->templates );

   // Add the modified cache to allow WordPress to pick it up for listing
   // available templates
   wp_cache_add( $cache_key, $templates, 'themes', 1800 );

   return $atts;

 }

 /**
  * Checks if the template is assigned to the page
  */
 public function view_project_template( $template ) {

   // Get global post
   global $post;

   // Return template if post is empty
   if ( ! $post ) {
     return $template;
   }

   // Return default template if we don't have a custom one defined
   if ( ! isset( $this->templates[get_post_meta(
     $post->ID, '_wp_page_template', true
   )] ) ) {
     return $template;
   }

   $file = plugin_dir_path( __FILE__ ). get_post_meta(
     $post->ID, '_wp_page_template', true
   );

   // Just to be safe, we check if the file exist first
   if ( file_exists( $file ) ) {
     return $file;
   } else {
     echo $file;
   }

   // Return template
   return $template;

 }

}
add_action( 'plugins_loaded', array( 'PageTemplater', 'get_instance' ) );