The command line you use to start the database server is:
dbeng16.exe -c 8m -n xxx "G:\DEMOS\DB\xxx_16.db"
That means that the connection parms should be
ServerName=xxx
DatabaseName=xxx_16
The connection parameters for dbping uses connection parm values that correctly match the start command for the database server. However, the connection string used by PHP uses
ServerName=kww
DatabaseName=kww_16