wp_new_user_notification( int $user_id, null $deprecated = null, string $notify = '' )

function wp_new_user_notification( $user_id, $deprecated = null, $notify = '' ) {
	if ( $deprecated !== null ) {
		_deprecated_argument( __FUNCTION__, 'WP-4.3.1' );
	}

	global $wpdb, $wp_hasher;
	$user = get_userdata( $user_id );

	// The blogname option is escaped with esc_html on the way into the database in sanitize_option
	// we want to reverse this for the plain text arena of emails.
	$blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);

	if ( 'user' !== $notify ) {
		$switched_locale = switch_to_locale( get_locale() );

		/* translators: %s: site title */
		$message  = sprintf( __( 'New user registration on your site %s:' ), $blogname ) . "\r\n\r\n";
		/* translators: %s: user login */
		$message .= sprintf( __( 'Username: %s' ), $user->user_login ) . "\r\n\r\n";
		/* translators: %s: user email address */
		$message .= sprintf( __( 'Email: %s' ), $user->user_email ) . "\r\n";

		$wp_new_user_notification_email_admin = array(
			'to'      => get_option( 'admin_email' ),
			/* translators: Password change notification email subject. %s: Site title */
			'subject' => __( '[%s] New User Registration' ),
			'message' => $message,
			'headers' => '',
		);

		/**
		 * Filters the contents of the new user notification email sent to the site admin.
		 *
		 * @since WP-4.9.0
		 *
		 * @param array   $wp_new_user_notification_email {
		 *     Used to build wp_mail().
		 *
		 *     @type string $to      The intended recipient - site admin email address.
		 *     @type string $subject The subject of the email.
		 *     @type string $message The body of the email.
		 *     @type string $headers The headers of the email.
		 * }
		 * @param WP_User $user     User object for new user.
		 * @param string  $blogname The site title.
		 */
		$wp_new_user_notification_email_admin = apply_filters( 'wp_new_user_notification_email_admin', $wp_new_user_notification_email_admin, $user, $blogname );

		@wp_mail(
			$wp_new_user_notification_email_admin['to'],
			wp_specialchars_decode( sprintf( $wp_new_user_notification_email_admin['subject'], $blogname ) ),
			$wp_new_user_notification_email_admin['message'],
			$wp_new_user_notification_email_admin['headers']
		);

		if ( $switched_locale ) {
			restore_previous_locale();
		}
	}

	// `$deprecated was pre-4.3 `$plaintext_pass`. An empty `$plaintext_pass` didn't sent a user notification.
	if ( 'admin' === $notify || ( empty( $deprecated ) && empty( $notify ) ) ) {
		return;
	}

	// Generate something random for a password reset key.
	$key = wp_generate_password( 20, false );

	/** This action is documented in wp-login.php */
	do_action( 'retrieve_password_key', $user->user_login, $key );

	// Now insert the key, hashed, into the DB.
	if ( empty( $wp_hasher ) ) {
		require_once ABSPATH . WPINC . '/class-phpass.php';
		$wp_hasher = new PasswordHash( 8, true );
	}
	$hashed = time() . ':' . $wp_hasher->HashPassword( $key );
	$wpdb->update( $wpdb->users, array( 'user_activation_key' => $hashed ), array( 'user_login' => $user->user_login ) );

	$switched_locale = switch_to_locale( get_user_locale( $user ) );

	/* translators: %s: user login */
	$message = sprintf(__('Username: %s'), $user->user_login) . "\r\n\r\n";
	$message .= __('To set your password, visit the following address:') . "\r\n\r\n";
	$message .= network_site_url("wp-login.php?action=rp&key=$key&login=" . rawurlencode($user->user_login), 'login') . "\r\n\r\n";

	$message .= wp_login_url() . "\r\n";

	$wp_new_user_notification_email = array(
		'to'      => $user->user_email,
		/* translators: Password change notification email subject. %s: Site title */
		'subject' => __( '[%s] Your username and password info' ),
		'message' => $message,
		'headers' => '',
	);

	/**
	 * Filters the contents of the new user notification email sent to the new user.
	 *
	 * @since WP-4.9.0
	 *
	 * @param array   $wp_new_user_notification_email {
	 *     Used to build wp_mail().
	 *
	 *     @type string $to      The intended recipient - New user email address.
	 *     @type string $subject The subject of the email.
	 *     @type string $message The body of the email.
	 *     @type string $headers The headers of the email.
	 * }
	 * @param WP_User $user     User object for new user.
	 * @param string  $blogname The site title.
	 */
	$wp_new_user_notification_email = apply_filters( 'wp_new_user_notification_email', $wp_new_user_notification_email, $user, $blogname );

	wp_mail(
		$wp_new_user_notification_email['to'],
		wp_specialchars_decode( sprintf( $wp_new_user_notification_email['subject'], $blogname ) ),
		$wp_new_user_notification_email['message'],
		$wp_new_user_notification_email['headers']
	);

	if ( $switched_locale ) {
		restore_previous_locale();
	}
}