Displays WHERE for two conditions in the same column - php

Question

-----------------------------------------------------
| id | posts_id | users_id | ratings |
-----------------------------------------------------
| 1 | 7 | 20 | 5 |
| 2 | 8 | 20 | 3 |
| 3 | 7 | 21 | 4 |
-----------------------------------------------------
Table name: mytable
\I want to make sure that ratings between posts_id and users_id are matched on the same column.
$query = $conn->query("SELECT ratings FROM mytable WHERE posts_id=7 and users_id=20");
$row = $query->fetch_array();
echo $row['ratings'];
This query does not work. I know there must be something wrong.
I want to get results: 5
What is the best query to show ratings?
----------------UPDATE-----------------------------
Sorry, my first problem lies with the connection, and now it is resolved.
But now there is a new problem.
I want to display the total sum of the rating results.
My new code
$Rate = $conn->query("SELECT * FROM mytable WHERE posts_id=7");
while ($Rated = $Rate->fetch_array()) {
echo $Rated['ratings'] + $Rated['ratings'];
}
For example on posts_id=7
Here I expect 5 + 4 = 9
But my code results exactly 54 + 54
How to fix this code?

Answer 1

For the updated question, this code should be work. We can use sum() function. Check here sum() function
$Rate = $conn->query("SELECT sum(ratings) as ratings FROM mytable WHERE posts_id=7");
while ($Rated = $Rate->fetch_array()) {
echo $Rated['ratings'];
}