int $isolation = pq\Transaction::READ_COMMITTED[, bool $readonly = FALSE[, bool $deferrable = FALSE]]])Asynchronously begin a transaction.
int $isolation# = pq\Transaction::READ_COMMITTEDbool $readonly# = FALSEbool $deferrable# = FALSENOTE:
A transaction can only be deferrable if it also is readonly and serializable.
See the official PostgreSQL documentation for further information.