title: query error displaying unknown message
body: <p>Can you please help me with this error?</p>
  
  <p>Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in on line 17</p>
  
  <p>Here is the code,</p>
  
  <pre><code>$query="SELECT * FROM users WHERE id ='$adminID' AND role id = '2'";
  $result = mysqli_query($db_connection, $query);
  $num=mysqli_num_rows($result);  &lt;--line 17
  </code></pre>