I am trying to execute the following query using a PDO Prepared Statement, but when I call $query->fetch();
it throws an exception SQLSTATE[HY000]: General
You would be correct in that PDO (and I believe any PHP method?) does not allow for multiple queries in a single by default. There are some workarounds which you can read about more, such as:
PDO support for multiple queries (PDO_MYSQL, PDO_MYSQLND)
but they do increase the risk of SQL injection so it is ill-advised.