"Enabling Required PHP Modules "gmp" and "bcmath" for WebAuthn Passwordless Authentication"¶

You can try, this might fix it...

sudo apt-get install php8.1-gmp php8.1-bcmath
sudo systemctl restart apache2

else ...

The PHP modules "gmp" and/or "bcmath" are not enabled. If you use WebAuthn passwordless authentication, these modules are required.

If you see this error message, it means that you need to enable the "gmp" and/or "bcmath" PHP modules on your server. These modules are required for WebAuthn passwordless authentication to work properly.

To enable the "gmp" module, you can follow these steps:

Open your php.ini file. This file is usually located in /etc/php.ini or /etc/php/#.#/apache2/php.ini.

nano /etc/php/8.1/apache2/php.ini

Uncomment the line extension=gmp by removing the semicolon (;) at the beginning of the line.
Uncomment the line extension=bcmath by removing the semicolon (;) at the beginning of the line.

Note: if extension=bcmath is missing add it

Save and close the file.

Restart your web server.

sudo service apache2 restart

---

If the line is Missing ad it at the end of the file.

---

After the restart, check that the changes have been applied by running the following command:

php -m

This will display a list of enabled PHP modules. If "gmp" and/or "bcmath" are not in the list, then there may be an issue with the installation of the modules.

If gmp is not listed in the output of php -m, then it means that the gmp module is not currently enabled in your PHP configuration.

To install the gmp PHP extension on Ubuntu 22.04.2 LTS, you can follow these steps:

Open a terminal window.

Install the gmp library and the PHP gmp extension using the following command:

sudo apt-get install php-gmp

even though you shouldn't have to I have had to reboot service to get this to take effect.