$query   = "INSERT INTO log (ip) VALUES (:ip) ";

$result  = $connexion->prepare("$query");  

$result->execute(array(':ip' => $ip ));  

//

$id = $connexion->lastInsertId();

$connexion->beginTransaction(); // DEBUT TRANSACTION



$query  = "INSERT INTO log (ip) VALUES (:ip) ";

$result  = $connexion->prepare("$query");  

$result->execute(array(':ip' => $ip ));  

//

$id = $connexion->lastInsertId();



$connexion->commit(); // FIN TRANSACTION

Citation :For LAST_INSERT_ID(), the most recently generated ID is maintained in the server on a per-connection basis. It is not changed by another client. It is not even changed if you update another AUTO_INCREMENT column with a nonmagic value (that is, a value that is not NULL and not 0). Using LAST_INSERT_ID() and AUTO_INCREMENT columns simultaneously from multiple clients is perfectly valid. Each client will receive the last inserted ID for the last statement that client executed.