Is isset() here right? / or is my if-condition wrong?

Question

i am making a Tube-Site and I can´t finish my code. At the moment I am working on a Favorize-Script, so registered people can "favorize" videos and can see them on a special site.

Logically it should not be possible to favorize a video twice and that´s my problem at the moment.

But I think my if-condition is wrong because it doesn´t check if the userid and the videoid exist!

Here is my code:

<?php
 session_start();
 include('config.php');

    $videoid = $_GET['id'];
    $userid = $_SESSION["username"];

    $result = mysql_query("SELECT `id` FROM `users` WHERE `username` = '$userid'") or die (mysql_error());
    $row = mysql_fetch_assoc($result);
    $usernameid = $row['id'];

    if (isset($userid, $videoid))
    {
    $row = "INSERT INTO favorites (userid, videoid, time)
    VALUES
    ('$usernameid','$videoid', now())";

    mysql_query("$row");

    header ("Location: http://localhost/video.php?id=" . $_GET['id'] . ""); 
    } 
    else
    {
    header ("Location: http://localhost/video.php?id=" . $_GET['id'] . "");
    }


?>

My Favorites-Table: favoriteid | userid | videoid | time

So it should check everytime if a video and a username is already set.

I also tried !isset but it doesn´t works

Answer 1

Change:

if (isset($userid, $videoid))

for:

if (isset($userid) && isset($videoid))

Answer 2

UPDATE

if($userid != '' && $videoid != ''){
    $check = mysql_query("SELECT * FROM `favorites` WHERE `userid` = '$usernameid' AND `videoid` = '$videoid'");

    if (mysql_num_rows($check) == 0) {
        $row = "INSERT INTO favorites (userid, videoid, time)
        VALUES ('$usernameid','$videoid', now())";

        mysql_query("$row");

        header ("Location: http://localhost/video.php?id=" . $_GET['id'] . ""); 
    }else{
        echo "You've already voted!";
    }
}else{
    header("Location: http://localhost/");
}

Answer 3

You should consider looking into MySQLI since mysql_* functions are slowly being deprecated.

Anyhow you should use a function called mysql_num_rows and check if the result is either 0 or 1. If the returning result is 1 you will know the video is already favourited and shouldn't repeat the action. If you get a 0 then insert it!

if (mysql_num_rows($result) == 0 && isset($userid) && isset($videoid)) {
$row = "INSERT INTO favorites (userid, videoid, time)
VALUES ('$usernameid','$videoid', now())";

    mysql_query("$row");

    header ("Location: http://localhost/video.php?id=" . $_GET['id'] . ""); 
}