I created several queries like this one $reponse = $bdd->query('SELECT * FROM jeux_video'); and if i don't put the closeCursor() statement after each one, no error appears... So, in which cases closeCursor() is useful ?
As per the manual:
PDOStatement::closeCursor() frees up the connection to the server so that other SQL statements may be issued, but leaves the statement in a state that enables it to be executed again.
This method is useful for database drivers that do not support executing a PDOStatement object when a previously executed PDOStatement object still has unfetched rows. If your database driver suffers from this limitation, the problem may manifest itself in an out-of-sequence error.
See, if that helps you in better understanding the use of close cursor.