mysqli与mysql的区别是什么？

$conn = mysqli_connect('localhost', 'root', '123', 'db_test') or ('error');

$sql = "select * from db_table";

$query = mysqli_query($conn,$sql);

while($row = mysqli_fetch_array($query)){

    echo $row['title'];

}

$conn = mysqli('localhost', 'root', '123', 'db_test');

$sql = "select * from db_table";

$query = $conn->query($sql);

while($row = $query->fetch_array()){

    echo $row['title'];

}