Run plugin code from "functions.php" in WordPress - wordpress

Question

I have a plugin for allowing duplicate emails on registration and that is working fine if I have used the plugin. I want to use plugin code in functions.php (meaning to say run the plugin code functionality with themes).
Below is my plugin code:
/**
* Plugin Name: Allow duplicate emails on registration
* Plugin URI: http://wordpress.stackexchange.com/a/125129/26350
*/
add_action( 'plugins_loaded', array( 'Allow_Duplicate_Emails_Registration', 'get_instance' ) );
class Allow_Duplicate_Emails_Registratn
{
private $rand = '';
static private $instance = NULL;
static public function get_instance()
{
if ( NULL === self::$instance )
self::$instance = new self;
return self::$instance;
}
public function __construct()
{
// Generate some random string:
$this->rand = '_remove_' . rand( 0, 99999);
add_filter( 'user_registration_email', array( $this, 'user_registration_email' ) );
add_action( 'user_register', array( $this, 'user_register' ) );
}
public function user_registration_email( $user_email )
{
// inject random string into the email
$user_email = str_replace( '#', $this->rand . '#', $user_email );
return $user_email;
}
public function user_register( $user_id )
{
// retrieve the newly registered user object
$user = get_user_by( 'id', $user_id );
// remove the random string
$user_email = str_replace( $this->rand . '#', '#', $user->user_email );
// update the email of the newly registered user
$args = array(
'ID' => $user_id,
'user_email' => $user_email,
);
$result = wp_update_user( $args );
}
}
And I have changed the above code below and put in functions.php, but it is not working:
add_action( 'init', array( 'Allow_Duplicate_Emails_Registration', 'get_instance' ) );

Answer 1

I have solved the problem. Add the below code in the wp-content/themes/my-themes/functions.php file:
<?php
add_filter( 'user_registration_email', array( $this, 'user_registration_email' ) );
add_action( 'user_register', array( $this, 'user_register' ) );
function user_registration_email( $user_email )
{
// Inject a random string into the email
$user_email = str_replace( '#', $this->rand . '#', $user_email );
return $user_email;
}
function user_register( $user_id )
{
// Retrieve the newly registered user object
$user = get_user_by( 'id', $user_id );
// Remove the random string
$user_email = str_replace( $this->rand . '#', '#', $user->user_email );
// Update the email of the newly registered user
$args = array(
'ID' => $user_id,
'user_email' => $user_email,
);
$result = wp_update_user( $args );
}
?>