Begins a transaction.
trans_args can be a combination of IBASE_READ, IBASE_WRITE, IBASE_COMMITTED, IBASE_CONSISTENCY, IBASE_CONCURRENCY, IBASE_REC_VERSION, IBASE_REC_NO_VERSION, IBASE_WAIT and IBASE_NOWAIT.
Note: The behaviour of this function has been changed in PHP 5.0.0. The first call to ibase_trans() will not return the default transaction of a connection. All transactions started by ibase_trans() will be rolled back at the end of the script if they were not committed or rolled back by either ibase_commit() or ibase_rollback().
Note: In PHP 5.0.0. and up, this function will accept multiple trans_args and link_identifier arguments. This allows transactions over multiple database connections, which are committed using a 2-phase commit algorithm. This means you can rely on the updates to either succeed in every database, or fail in every database. It does NOT mean you can use tables from different databases in the same query!