MySQL查询只返回pdo中的一行

My MySQL query is displaying just one row (instead of all of the rows), but when I do a COUNT on the query, it shows the correct number of rows in the query. What seems to be the problem here?

$sql5 = "SELECT m.*, i.*, COUNT(*) AS num, m.id AS m_id FROM members m JOIN roommate_seek i ON m.id = i.member_id
              WHERE _school = :school AND i.category = :category";

foreach ($db->query($sql5, array('school' => $_GET['school'], 'category' => $category)) AS $result3)
{
    echo "{$result3['m_id']}";
}

You are using an aggregate function (COUNT) without GROUP BY. In that case it is suppose to return exactly one row.