Create Template Page WordPress

class-template-page.php

Class TemplatePage
{
	public function __construct()
	{
		$this->templates = array();
		if ( version_compare( floatval( get_bloginfo( 'version' ) ), '4.7', '<' ) ) {
			add_filter('page_attributes_dropdown_pages_args',array( $this, 'register' ));
		} else {
			add_filter('theme_page_templates', array( $this, 'create' ));
		}
		add_filter('wp_insert_post_data',array( $this, 'register' ));
		add_filter('template_include',array( $this, 'view'));

		$this->templates = array(
			// 'main.php' => __( 'LSDDonation - Main', 'lsddonation' ),
			'payment.php' => __( 'LSDDonation - Payment', 'lsddonation' ),
		); 
	}

	public function create( $posts_templates )
	{
		$posts_templates = array_merge( $posts_templates, $this->templates );
		return $posts_templates;
	}

	public function register( $atts ) {
		$cache_key = 'page_templates-' . md5( get_theme_root() . '/' . get_stylesheet() );

		$templates = wp_get_theme()->get_page_templates();
		if ( empty( $templates ) ) {
			$templates = array();
		}

		wp_cache_delete( $cache_key , 'lsddonation');
		$templates = array_merge( $templates, $this->templates );
		wp_cache_add( $cache_key, $templates, 'lsddonation', 1800 );

		return $atts;
	}

	public function view( $template ) {
		if ( is_search() ) {
			return $template;
		}

		global $post;
		if ( ! $post ) {
			return $template;
		}

		if ( ! isset( $this->templates[get_post_meta(
			$post->ID, '_wp_page_template', true
		)] ) ) {
			return $template;
		}

		// Allows filtering of file path
		$filepath = apply_filters( 'page_templater_plugin_dir_path', plugin_dir_path( __FILE__ ) );

		$file = LSDD_PATH . 'public/templates/' . 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;
	}
}
new TemplatePage;