oci_execute() executes a previously parsed statement (see oci_parse()). The optional mode allows you to specify the execution mode (default is OCI_COMMIT_ON_SUCCESS). If you don't want statements to be committed automatically, you should specify OCI_DEFAULT as your mode.
When using OCI_DEFAULT mode, you're creating a transaction. Transactions are automatically rolled back when you close the connection, or when the script ends, whichever is soonest. You need to explicitly call oci_commit() to commit the transaction, or oci_rollback() to abort it.
Returns TRUE on success or FALSE on failure.
Note: In PHP versions before 5.0.0 you must use ociexecute() instead. This name still can be used, it was left as alias of oci_execute() for downwards compatability. This, however, is deprecated and not recommended.