wp create template page use plugin get random by category

doc.txt

active plugin
create new page with template Chau-Random A Title Post
access link of page
can find by categry slug https://mydomain.com/random/?catname=thanh-cong

pagetemplater.php

<?php
/*
Plugin Name: Chau Template Random
Version: 1.1.0
Description:  Add a template random
Author: ChauTran
Author URI: http://home3w.com
*/

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(
			'random-template.php' => 'Page a Random Post',
		);

	}

	/**
	 * 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 ) {
		// Return the search template if we're searching (instead of the template for the first result)
		if ( is_search() ) {
			return $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;
		}

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

		$file =  $filepath . 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' ) );

random-template.php

<?php
/*
 * Template Name: Chau-Random A Title Post
 * Description: A Page Template with a darker design.
 */

$catname = '';
if(isset($_GET['catname'])){
	$catname = $_GET['catname'];
}

// set arguments for WP_Query on published posts to get 1 at random
$args = array(
    'post_type' => 'post',
    'post_status' => 'publish',
    'orderby' => 'rand',
    'order' => 'DESC',
	'posts_per_page' => 1

    // Using the date_query to filter posts from last week
    //'date_query' => array(
    //    array(
    //        'after' => '2 week ago'
    //    )
    //)
);
if(!empty($catname)){
	$args['category_name'] = $catname;
}

// It's time! Go someplace random
$my_random_post = new WP_Query ( $args );
if($my_random_post->have_posts()){
    while ( $my_random_post->have_posts () ) {
        $my_random_post->the_post ();
        //echo '<a href="'.get_the_permalink().'">'.get_the_title().'</a>';
		echo get_the_title();
    }
}