Different way for php and jquery for better work

I am new here and I learned a lot on w3 schools and similar websites about languages. Now I have few question for you guys. Questions are small so I will ask two in one asking:

For php: What is the best different way for security reasons by getting data by post or get.

$post_id = mysqli_real_escape_string($con, $_POST['id']);

$get_id = mysqli_real_escape_string($con, $_GET['id']);

For jquery: What is best different way for getting info from database without reload or is there anyone.

setInterval(function(){
        $('#container').load('file.php')
    }, 1000);