Getting News Feed (Social Media) - php

Question

I am currently developing a social media app which includes users (you can add them as friend) and posts (text, image etc...)
I want to show to user 5 newest posts compared to user's posts and user's friends' posts when user enters to the app.
I know this is not the wisest method to achieve this but so far i did this. Query returned only one post while there are more and its not even newest nor oldest. I think the problem is in "OR" clause.
I get all sno's of friends of user and put in WHERE clause one by one with "OR" clause.
//CURRENT FRIENDS
$sql = 'SELECT current AS currents FROM friends WHERE sno = :sno';
$query = $this -> conn -> prepare($sql);
$query -> execute(array(':sno' => $usersSno));
$friends = $query -> fetchObject() -> currents;
//SELECT 5 NEWEST POST
$sql = 'SELECT operationId FROM posts WHERE operationId = :operationId';
$array = array(':operationId' => $usersSno);
if(isset($friends)) {
$ids = explode(",", $friends);
for($i = 0; $i < count($ids); $i++) {
$sql = $sql.' OR operationId = :operationId'.$i;
$array[':operationId'.$i] = $ids[$i];
}
}
if($from == null)
$sql = $sql.' ORDER BY operationId DESC LIMIT 5';
else {
$sql = $sql.' AND operationId < :from ORDER BY operationId DESC LIMIT 5';
$array[':from'] = $from;
}
$query = $this -> conn -> prepare($sql);
$query -> execute($array);
$result = $query -> fetchAll(PDO::FETCH_ASSOC);
User's sno is 1 and user has two friends which their sno's are 2 and 75.
echo $sql;
SELECT operationId FROM posts WHERE operationId = :operationId OR operationId = :operationId0 OR operationId = :operationId1 ORDER BY operationId DESC LIMIT 5
print_r($array);
Array
(
[:operationId] => 1
[:operationId0] => 2
[:operationId1] => 75
)

Answer 1

I feel like a stupid for realizing my mistake right after starting a bounty for it. I should've use WHERE sno (since i've been getting posts from user's id [sno]) not WHERE operationId in $sql
So echo $sql; be like:
SELECT operationId FROM posts WHERE sno = :sno OR sno = :sno0 OR sno = :sno1 ORDER BY operationId DESC LIMIT 5
And print_r($array) is:
Array
(
[:sno] => 1
[:sno0] => 2
[:sno1] => 75
)
At least i am happy to resolve this problem and even resolving it my own :)
EDIT: I noticed two logical error too in my sql query.
1- Comparing date string with operationId of post
I am comparing posts with their dates (you can also compare with operationId of post) to see which one is newest. But in the code i compared operationId with $from variable (which is a date string).
So final code;
$sql = $sql.') AND createdAt < :from ORDER BY operationId DESC LIMIT 5';
2- OR clauses should be separeted with AND clause by parentheses.
start of parenthese
$sql = 'SELECT operationId FROM posts WHERE (sno= :sno';
end of parenthese
if($from == null)
$sql = $sql.') ORDER BY operationId DESC LIMIT 5';
else {
$sql = $sql.') AND createdAt < :from ORDER BY operationId DESC LIMIT 5';
$array[':from'] = $from;
}