Checking result count - mysql

Question

I am working on a project that requires getting posts from my database. I am trying to get the posts that are posted by the user and other users unless they are private.
My SQL query is
SELECT . . .,COUNT(F.user_id) AS is_following FROM posts AS P INNER JOIN users AS U ON U.id = P.user_id LEFT JOIN followers AS F ON F.user_id = :userid AND F.following_id = U.id WHERE *If matches search* AND U.private = 0 OR U.id = :userid OR is_following = 1 ORDER BY. . .
I am selecting where the user is following the posters and counting it if 0 it means they are not following and 1 would mean 1 result, therefore, following them. Also I am checking if private is 0 meaning the account is public.
The problem is while I have the is_following = 1 it returns no results if I remove it though it does return results but not all.
Tables:
users: id|username|private|...
followers: userid|followingid
posts: id|userid|body
Content:
users:
user1|test1|1 (This is the user running the request)
user2|test2|1
user3|test3|1
followers:
user1|user2 (User searching follows test2)
posts:
post1|user1|HelloWorld
post2|user2|Hello_World
post3|user3|Hello-World
The expected outcome is to return post1 and post2 but not post3 since user3 is private (private is set to true/1) and user1 does no follow test3, but it should display user2's post since user1 follows user2

Answer 1

If I understand correct.
There are two kinds of groups
private is 0 meaning the account is public
private is 1 need to find the following User on followers table.
A simple way you can make two query one is for private is 0 , another is for private is 1 ,then use UNION ALL combine those.
SELECT * FROM
(
SELECT p.*
FROM users as u
INNER JOIN posts AS P ON p.userid = u.id
WHERE u.private = 0
UNION ALL
SELECT p.*
FROM users as u
INNER JOIN posts AS P ON p.userid = u.id
RIGHT JOIN followers AS F ON F.followingid = u.id
WHERE u.private = 1 AND f.userid = :userid
)t
Or use exists to check it
SELECT p.*
FROM users as u
INNER JOIN posts AS P ON p.userid = u.id
WHERE u.private = 0 OR exists
(
SELECT 1
FROM followers AS F LEFT JOIN users ON F.followingid = users.id
WHERE u.id = users.id
and users.private
and f.userid = :userid
)
sqlfiddle:http://sqlfiddle.com/#!9/50ef05/1
EDIT
if you want to get the user is or isn't is_following,you could follow like this.
then you could find which user have been is_following on outer where clause .
SELECT * FROM
(
SELECT p.*,0 as 'is_following'
FROM users as u
INNER JOIN posts AS P ON p.userid = u.id
WHERE u.private = 0
UNION ALL
SELECT p.*,1
FROM users as u
INNER JOIN posts AS P ON p.userid = u.id
RIGHT JOIN followers AS F ON F.followingid = u.id
WHERE u.private = 1 AND f.userid = 'user1'
)t
/*where is_following = 1*/
sqlfiddle:http://sqlfiddle.com/#!9/b7f6c/10

Answer 2

The reason it returns no results when you have the is_following condition is that you are trying to use an alias in a WHERE clause which is not permitted by MySQL. Replace is_following with COUNT(F.user_id) and it should work.