<?php
            defined( 'ABSPATH' ) or die( 'No script kiddies please!' );
            define( 'MY_PLUGIN_PATH', plugin_dir_path( __FILE__ ) );
            define( 'MY_PLUGIN_URL', plugin_dir_url( __FILE__ ) );
            register_activation_hook(__FILE__,'my_plugin_install');
            register_deactivation_hook( __FILE__, 'my_plugin_remove' );
            function my_plugin_install() {
                global $wpdb;
                $the_page_title = 'TEST';
                $the_page_name = 'test';
                delete_option("my_plugin_page_title");
                add_option("my_plugin_page_title", $the_page_title, '', 'yes');
                delete_option("my_plugin_page_name");
                add_option("my_plugin_page_name", $the_page_name, '', 'yes');
                delete_option("my_plugin_page_id");
                add_option("my_plugin_page_id", '0', '', 'yes');
                $the_page = get_page_by_title( $the_page_title );
                if ( ! $the_page ) {
                    $_p = array();
                    $_p['post_title'] = $the_page_title;
                    $_p['post_content'] = "";
                    $_p['post_status'] = 'publish';
                    $_p['post_type'] = 'page';
                    $_p['comment_status'] = 'closed';
                    $_p['ping_status'] = 'closed';
                    $_p['post_category'] = array(1);
                    $the_page_id = wp_insert_post( $_p );
                }
                else {
                    $the_page_id = $the_page->ID;
                    $the_page->post_status = 'publish';
                    $the_page_id = wp_update_post( $the_page );
                }
                delete_option( 'my_plugin_page_id' );
                add_option( 'my_plugin_page_id', $the_page_id );
            }
            function my_plugin_remove() {
                global $wpdb;
                $the_page_title = get_option("my_plugin_page_title");
                $the_page_name = get_option("my_plugin_page_name");
                $the_page_id = get_option('my_plugin_page_id');
                if( $the_page_id ){wp_delete_post( $the_page_id );}
                delete_option("my_plugin_page_title");
                delete_option("my_plugin_page_name");
                delete_option("my_plugin_page_id");
            }
            function custom_template($template){
                $template = plugin_dir_path( __FILE__ ) . 'my-custom-page.php';
                return $template;
            }
            if ( !is_admin() ) {
                if ( have_posts() ) {
                    while ( have_posts() ) {
                        the_post();
                        if(get_the_ID() == get_option('my_plugin_page_id')){
                            add_filter( 'template_include', 'custom_template' );
                        }
                    }
                }
            }
            ?>

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