If you are facing the error Call to undefined function mssql_connect() in Ubuntu / Linux, then you have to simply install php5-sybase to make this problem resolved.
Simply goto:
System -> Administration -> Synaptic Package Manager
And find the package or software as “php5-sybase“ or php sybase
and install the MS SQL Server module for PHP.
After successful installation, restart your Apache Server with the following command in the terminal:
sudo /etc/init.d/apache2 restart
And the problem is solved.
Or
goto gnome-terminal, and write the following command:
sudo apt-get install php5-sybase
(if php5 is not the version you’re using, then find that version’s php sybase package and install it)
After successful installation, restart your Apache Server with the following command:
sudo /etc/init.d/apache2 restart
And the problem is solved.