WordPress 插件开发 增加自定义页面类型及前端显示页面

最近想开发一个新的插件用来监控VPS库存情况，下面我们记录一下一些代码的细节片段。

这里写一下如何通过插件功能自定义某个页面的类型，前端显示时固定使用某个模板来显示。

<?php /* Plugin Name: JiLoc Test */  class PageTemplate {  	/** 	 * 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( 			'goodtobebad-template.php' => 'It's Good to Be Bad', 		); 			 	}   	/** 	 * 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( 'PageTemplate', 'get_instance' ) );