$handle = ora_plogon('scott@remotedb','tiger');

Always returns "ORA-12154: TNS:could not resolve service name" or similar errors indicating Oracle is not reading the TNSNAMES.ORA file.  Using sysinternals filemon to watch PHP accessing files shows the same result, the oracle drivers never read tnsnames.ora when called from php.  SQLNET.log files indicate that PHP is always attempting to use the BEQLOCAL protocol adapter regardless of the tnsnames.ora settings.  Adding a ORACLE_SID environment variable caused php to try to connect to that SID at BEQLOCAL.

Users report that Oracle's SQLPLUS and external ODBC programs have no trouble accessing the remote db.  tnsping and other oracle test programs work correctly when called from a php passthru function, indicating that the environment is correct. 

This problem occurs using both OCI and ORACLE functions.

About a half dozen individuals on the php-db list have noted the same problem.  To date no one on the PHP-DB list has claimed to make php work with oracle under windows.  All the users report using php with an oracle 8.x.x client and the precompiled binaries supplied from the main php site. Many variations of ORACLE_HOME and other env variable settings have been tried.  

Under Unix php does not exhibit the same problem..