El $tns
la variable se ve mal.
Prueba
$tns = "(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=xyz.abc.us-west-2.rds.amazonaws.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=orcl)));";
El $tns
la variable se ve mal.
Prueba
$tns = "(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=xyz.abc.us-west-2.rds.amazonaws.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=orcl)));";