Array to string conversion error - php

Question

I have a query that's pulling a list of IDs. Those IDs are in an array and I need to search another table with those IDs. I tried using implode to make those IDs a string that I could use in a where clause but I keep getting this error.
My current code is:
$query = $this->db->query('
SELECT *
FROM system_scoperights
WHERE user = '. $this->session->userdata('username') .'
');
foreach ($query->result() as $row) {
$scope = $row->site;
$data[] = $scope;
}
$dataScope[] = $data;
$idList = implode(',', $dataScope); <---- Error Line
$where = 'WHERE scope_scopes.sc_ID IN '. $idList .'';
I've tried different things I found on forums like:
$idList = implode(',', array_values($dataScope));
and
$idList = implode(',', join($dataScope));
but none of those work. (I've never even heard of the join function)
Thanks in advance for the help.

Answer 1

$dataScope[] = $data;
but
$data[] = $scope;
therefore $dataScope has an array inside it's array. implode only work on one level, so that why you're getting this error.
You should note that this is actually possible in SQL:
SELECT * FROM some_table WHERE id IN (SELECT site FROM another_table WHERE ... )
which would eliminate the entire need for this code.
That is:
$where = 'WHERE scope_scopes.sc_ID IN (SELECT site
FROM system_scoperights
WHERE user = '. $this->session->userdata('username') . ')';

Answer 2

I partially agree with Jay's answer...just remove the line:
$dataScope[] = $data
and use the $data variable directly since it's already an array:
$idList = implode(',', $data);
However you also should use ( and ) in your where clause:
$where = 'WHERE scope_scopes.sc_ID IN (' . $idList . ')';
Using sub-queries in your where clauses, although they do have their place at times, can cost a lot of overhead, especially using 'SELECT *'. Never ask for more than you need from your db tables :)