The Oracle functions provide an alternative to the OCI8 functions, also available in PHP. Unlike OCI8, these functions can be used to access Oracle databases prior to version 8i. However, if you are accessing Oracle 8i databases, the OCI8 functions provide better functionality and a performance increase. To compile Oracle support into PHP, use the --with-oracle flag when calling the PHP configuration program. Don't forget to set the ORACLE_HOME and ORACLE_SID environment variables. Normally these variables are set already with an Oracle installation. If not, check with your database administrator, who should be able to provide you with the necessary values.