许多mysqli连接关闭？

Question

I have a php that I need to many selects, like 10, so I do:

$stmt = $mysqli_->prepare("SELECT count(id) as num FROM table WHERE id=?");
$stmt->bind_param('i', $id);
$stmt->execute();
$stmt->bind_result($count);
$stmt->fetch();
$stmt->close();

$stmt = $mysqli_->prepare("SELECT count(id) as num FROM table2 WHERE id=?");
$stmt->bind_param('i', $id);
$stmt->execute();
$stmt->bind_result($count2);
$stmt->fetch();
$stmt->close();

$stmt = $mysqli_->prepare("SELECT count(id) as num FROM table3 WHERE id=?");
$stmt->bind_param('i', $id);
$stmt->execute();
$stmt->bind_result($count3);
$stmt->fetch();
$stmt->close();

...

is it ok to use the $stmt->close(); all the time or would it kill the connection performance?