Mysql PDO insert

$sql ='INSERT INTO table(id,a1,a2)VALUES(1,1,1),(2,2,2),(3,3,3)';
mysqli_query($link,$sql);

$stmt = $mysqli->prepare('INSERT INTO `table`(`id`,`a1`,`a2`)VALUES(:id,:a1,:a2)');
$stmt->bindParam(':id', $id, PDO::PARAM_INT);
$stmt->bindParam(':a1', $a1, PDO::PARAM_INT);
$stmt->bindParam(':a2', $a2, PDO::PARAM_INT);

$id = 1;
$a1= 1;
$a2= 1;
$stmt->execute();

$id = 2;
$a1= 2;
$a2= 2;
$stmt->execute();

$id = 3;
$a1= 3;
$a2= 3;
$stmt->execute();