title: mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource
body: <p>I am trying to select data from a MySQL table, but I get one of the following error messages:</p>
  
  <blockquote>
    <p>mysql_fetch_array() expects parameter 1 to be resource, boolean given</p>
  </blockquote>
  
  <p>This is my code:</p>
  
  <pre><code>$username = $_POST['username'];
  $password = $_POST['password'];
  
  $result = mysql_query('SELECT * FROM Users WHERE UserName LIKE $username');
  
  while($row = mysql_fetch_array($result)) {
      echo $row['FirstName'];
  }
  </code></pre>