我应该通过ajax函数传递会话变量还是直接在脚本中访问它？

Question

I have a page that uses an ajax function to get updates from another page.The function uses the user's id, which is retrieved from a session variable to find any updates, which is then displayed in a "Updates" div. While my script is working currently, i find myself wondering if i could retrieve the userid stored in the session variable in my Ajax page instead of passing the userid through the ajax function. Are there any advantages and/or disadvantages to passing the userid through the ajax function instead of accessing it directly in the ajax script?

My Ajax function:

function FetchUpdate()
{
    var userid= <?php echo $_SESSION['UserID'] ?>;
    $.ajax(
    {
        type:"POST",
        url:"getupdates.php",
        data:{userid:userid}
    })

    .done(function(data){
        $("#Updates").html(data);
        setTimeout(FetchUpdate,1000*60);

    })

}

Ajax page(getupdates.php)

session_start();
$userid=$_SESSION['UserID'];
//fetches updates
//echos updates

Answer 1

This is an example approach of your situation:

Javascript :

function fetchUpdate(){
    var data = {}
        data.command = 'getUpdate'
    $.post('getupdates.php', data, function(result){
        var r = JSON.parse(result)
        try {
            if(r.status == true){
                console.log('Success! '+r.message)
            }else{
                console.log(r.message)
            }
        }catch(e){
            console.log(result)
        }
    })
}

PHP :

<?php
if(!isset($_SESSION)){$session = new Session();}
$uid = isset($_SESSION['userID']) ? $_SESSION['userID'] : 0;

if(isset($_POST['command'])){$cmd = $_POST['command']}

switch($cmd){
    case 'getUpdate':
    // Check $uid with database here.
        if($uid > 0){
            $response['status'] = true;
            $response['message'] = 'User details have been updated.';
        }else{
            $response['status'] = false
            $response['message'] = 'Invalid user.'
        }
    break;
    // Process other commands here.
}
// Return output
echo json_encode($response);

?>

Hope this helps!