$stmt = $dbh->prepare("insert into users (name,email,password) values (:name,:email,:password)"); //sql発行
$stmt->bindParam(":name", $name); //プレースホルダーを変数に結びつける
$stmt->bindParam(":email", $email);
$stmt->bindParam(":password", $password);

$name = "n10"; //変数に値を代入
$email = "e10";
$password = "p10";

$stmt->execute(); //実行

$name = "n10x";  //一部だけ変更し、後のデータは使い回して実行

$stmt->execute();

echo $dbh->lastInsertId();