How to pass variable to isset function in php? - php

Question

I am trying to return a $user_id variable from file to if(isset(...)) statement. I will perform a different if statement but just trying to echo out the $user_id variable to test that I am setting the page.
<?php
include 'core/init.php';
include 'init.image.php';
protect_page();
include 'includes/overall/overall_header.php';
if(isset($_GET['username']) === true && empty($_GET['username']) === false){
$username = $_GET['username'];
if(user_exists($username) === true){
$user_id = user_id_from_username($username);
$profile_data = user_data($user_id, 'first_name','last_name','email', 'username');
?>
<h1><?php echo $profile_data['first_name']; ?>'s Yor Page</h1>
<div id="navWrapper">
<ul>
<li>
<img src="uploads/profile/blank_profile.gif" width="150" height="150" id="blank_profile">
</li>
<nav>
<ul>
<li>
Albums
</li>
<li>
Music
</li>
</ul>
</nav>
</ul>
</div>
<?php
if(isset($_GET['action']) && $_GET['action']=='albums'){
$albums = get_profile_albums($user_id);
if(empty($albums)){
echo 'No Albums';
}else{
foreach($albums as $album){
if (empty($album['image'])) {
$album['image'] = 'uploads/profile/blank_profile.gif';
}
?>
<p><?php echo $album['name'],' (', $album['count'], ')'?> <br />
<a href="<?php echo $profile_data['username'];?>?action=album_id=<?php echo $album['id'];?>">
<img src="uploads/thumbs/<?php echo $album['id'];?>/<?php echo $album['image'];?>" />
</a><br />
<?php echo $album['description'];?>...<br />
</p>
<?php
}
}
}
if(isset($_GET['action']) && $_GET['action']=='album_id=$album['id']'){
echo $user_id;
}
if(isset($_GET['action']) && $_GET['action']=='music'){
echo'<h1>Music</h1>';
}
}else{
echo 'Sorry, that user doesn\'t exist';
}
}else{
header('Location: index.php');
exit();
}
include 'includes/overall/overall_footer.php';
?>

Answer 1

Single quotes do not parse the string but double quotes do. For example:
$album_id = 1;
echo 'album_id=$album_id ';
echo "album_id=$album_id";
Will result in album_id=$album_id album_id=1
Thus, $_GET['action']=='album_id=$album_id' is checking if $_GET['action'] is equal to 'album_id=$album_id' and not what $album_id is evaluated to.
Your check should be more along these lines:
if (/* ... */ && $_GET['action']=="album_id=$album_id") {
Edit: Suggestion.
You should check $_GET['action'] once and store $action. From there create an if/else if/else statement checking each possible type of action (music, albums, album, etc). If a type of action requires extra user supplied data, include that in the respective if block. For example:
$action = $_GET['action'];
// URL: /script.php?action=albums
if ($action == 'albums') {
// ...
}
// URL: /script.php?action=album&album_id=12
else if ($action == 'album') {
if (!empty($_GET['album_id'])) {
$album_id = $_GET['album_id'];
echo "User with id $user_id is trying to access album with id $album_id";
}
// ...
}
// ...
No more $_GET['action']=="album_id=$album_id"

Answer 2

You are passing the variable correctly.
What I'm more concerned with in the following line is:
if(isset($_GET['action']) && $_GET['action']=='album_id=$album_id'){
'album_id=$album_id' doesnt look right and is probably why your if is not firing... It looks like you're trying to use the variable $album_id wrapped in single quotes and that will not substitute the value and rather keep $album_id in tact. I'm not sure if this is what you intended but if not its likely the source of your problem.