How to do transactions between multiple database in a mysql server?

Below is my sequence of code

// global autocommit is 1

db->query('SET AUTOCOMMIT=0');
db->query('BEGIN');
db->query('INSERT INTO TRANSACTIONS (CREDIT) VALUES (150)');
db->chagngeDatabase('member');

// here autocommit become 1 automatically after Db change. And the previous query rollback automatically

db->query('INSERT INTO memberAccount(CREDIT) VALUES (150)');
db->query('COMMIT');

Whenever i’m trying to change the database then the autocommit value becomes 1 and its rollback my previous query. How to do transactions while changing the db between queries in same server?