update_user_caches example

$user = $wpdb->get_row(
            $wpdb->prepare(
                "SELECT * FROM $wpdb->users WHERE $db_field = %s LIMIT 1",
                $value
            )
        );
        if ( ! $user ) {
            return false;
        }

        update_user_caches( $user );

        return $user;
    }

    /** * Magic method for checking the existence of a certain custom field. * * @since 3.3.0 * * @param string $key User meta key to check if set. * @return bool Whether the given user meta key is set. */

$clean = _get_non_cached_ids( $user_ids, 'users' );

        if ( empty( $clean ) ) {
            return;
        }

        $list = implode( ',', $clean );

        $users = $wpdb->get_results( "SELECT * FROM $wpdb->users WHERE ID IN ($list)" );

        foreach ( $users as $user ) {
            update_user_caches( $user );
        }
    }
endif;

if ( ! function_exists( 'wp_mail' ) ) :
    /** * Sends an email, similar to PHP's mail function. * * A true return value does not automatically mean that the user received the * email successfully. It just only means that the method used was able to * process the request without any errors. * * The default content type is `text/plain` which does not allow using HTML. * However, you can set the content type of the email by using the * {@see 'wp_mail_content_type'} filter. * * The default charset is based on the charset used on the blog. The charset can * be set using the {@see 'wp_mail_charset'} filter. * * @since 1.2.1 * @since 5.5.0 is_email() is used for email validation, * instead of PHPMailer's default validator. * * @global PHPMailer\PHPMailer\PHPMailer $phpmailer * * @param string|string[] $to Array or comma-separated list of email addresses to send message. * @param string $subject Email subject. * @param string $message Message contents. * @param string|string[] $headers Optional. Additional headers. * @param string|string[] $attachments Optional. Paths to files to attach. * @return bool Whether the email was sent successfully. */