Using an array in a PHP MySQL WHERE clause - php

Question

Hi I am creating an array of user id's with a query. With another query I would like to select from a given table where the user_id is one that is in the array created from my very first query. How can I use an array in my WHERE clause?
Just for reference: $row_interest is the array
My Code:
//Grabs the user id's of the users that have the queried interest
$interest_search_query= "SELECT DISTINCT user_id FROM interests WHERE interest LIKE
'%".$search_term."%'";
$interest_search_result= mysqli_query($connect, $interest_search_query);
$row_interest= mysqli_fetch_array($interest_search_result);
//Grabs the user information with each user id
$search_query= "SELECT DISTINCT user_id, fname, lname, profile_pic, school FROM users
WHERE user_id IN $row_interest";
I tried "WHERE user_id IN $row_interest", but it doesn't seem to work. What could I be doing wrong?
Thanks.

Answer 1

$search_query= "SELECT DISTINCT user_id, fname, lname, profile_pic, school FROM users
WHERE user_id IN (".implode(',',$row_interest).")";

Answer 2

You can actually merge both queries.
SELECT distinct user_id, fname, lname, profile_pic, school
FROM users
WHERE user_id in
(SELECT distinct user_id from interests
where interest like %{search_term}%)

Answer 3

You could build an IN() clause for your SQL in PHP, but since the set is coming from another query you could use a JOIN to do this.
Edit:
I can't test this without your data, but the join would be something like
$search_query= "SELECT DISTINCT u.user_id, u.fname, u.lname, u.profile_pic, u.school
FROM user u
INNER JOIN interests i ON u.user_id = i.user_id
WHERE i.interest like '%".$search_term."%'";

Answer 4

It sounds like you could just use a join, but $row_interest is an array, and it is interpolated as "Array" in the query. It seems like you want to build the entire array first
$rows = array();
while ($row = mysqli_fetch_array($interest_search_result)) {
$rows[] = $row['user_id'];
}
Then you can create the "IN" clause you need.
"WHERE user ID IN (" . implode(",", $rows) . ")"
Your code is vulnerable to injection. You should properly parameterize the queries using prepared statements. This is more difficult to do with a variable number of arguments in mysqli as I understand it, but it is something to keep in mind.