I understand correctly, you need to add a section to:
/usr/local/cwpsrv/htdocs/resources/conf/php_switcher
and find the .ini file that correspond with the php version you want to install, in this example will be 7.2.ini
[pdo-firebird]
default=0
option="--with-pdo-firebird"
info-file=pdo-firebird.txt