Call to undefined function mssql_connect

I need to setup an Apache webserver that can query a Microsoft SQL (2005) database on another server using PHP. I installed Apache2 on an Ubuntu 20.04 LTS with the FreeTDS libraries for PHP 7.4 and I can query the remote database through the command line using the isql command, but if I try to connect through a PHP script trough a URL, I get a "Call to undefined function mssql_connect()" error on /var/log/apache2/error.log

I followed the steps listed here: https://askubuntu.com/questions/578934/mssql-connection-from-ubuntu

isql -v MSSQL devuser 'devpass' works so, according to the instructions "I'm golden!", but http://example.com/testsql.php throws the call to undefined function mssql_connect error.

Any help is greatly appreciated.