Mysql transactions within transactions

Question

In a PHP script working with a mysql database, I recently had the need to use a transaction at a point that happened to be inside another transaction. All my tests seem to

Answer 1

This page of the manual might interest you : 12.3.3. Statements That Cause an Implicit Commit; quoting a few sentences :

The statements listed in this section (and any synonyms for them) implicitly end a transaction, as if you had done a COMMIT before executing the statement.

And, a bit farther in the page :

Transaction-control and locking statements. BEGIN, LOCK TABLES, SET autocommit = 1 (if the value is not already 1), START TRANSACTION, UNLOCK TABLES.

See also this paragraph :

Transactions cannot be nested.
This is a consequence of the implicit commit performed for any current transaction when you issue a START TRANSACTION statement or one of its synonyms.