Why to use bindvalue in pdo code example

Example 1: bind in pdo

$sql = "SELECT * FROM myTable WHERE id = ?";
$stmt = $conn->prepare($sql);
$stmt->execute([$id]);

Example 2: bind in pdo

$sql = "SELECT * FROM myTable WHERE id = :id";
$stmt = $conn->prepare($sql);
$stmt->execute([":id"=>$id]);