show hyperlink only for a certain user's posts - php

Question

I have a posts table like this:
post_id user_id title date
12 1 abc 7/20/2014
13 1 cde 7/21/2014
14 2 fgh 7/22/2014
And a users table like this:
user_id username email password
1 name1 email1#domain.com ******
2 name2 email2#domain.com ******
The user_id in the posts table is the foreign key of the users table.
Note:
Assume that I store the user's session successfully by using $_SESSION['user_id'] .
Assume that I can echo all 3 post titles along with their usernames successfully too.
Now I would like to echo the edit hyperlink (Edit) for the post titles of a certain user, for example, user_id 1 or 2 after he's logged in. It means that if the user named name1 signs into his account and browses the post whose id is 14, he cannot see the edit hyperlink because it belongs to the another user named name2, whose session id, if any, should be unableable now, and vice versa.
For me, this is my code:
$q = "SELECT title, post_id, p.user_id AS currentuser
FROM posts AS p
INNER JOIN users AS u USING (user_id)
ORDER BY date ASC
";
$r = mysqli_query ($dbc, $q);
while ($row = mysqli_fetch_array($r, MYSQLI_ASSOC)) {
$uid = isset($_SESSION['user_id']);// variable for the seesion
$current_user = $row['currentuser'];// variable for the certain user ID
if($uid && $uid == $current_user){
echo " Edit </div>";
}
Then I test it, you know, it shows the edit hyperlink in every post title, but not what i expected.
Can you help? Thanks

Answer 1

$uid = isset($_SESSION['user_id']);
This results to either true or false. try
$uid = isset($_SESSION['user_id']) ? $_SESSION['user_id'] : -1;
What I did was use a ternary operator so if the session variable is set, you set it to it otherwise you set it to -1, which most probably does not exsist in a table id column