title: Array stores only one value instead of multiple
body: <p>I could not figure out how to solve this:</p>
  
  <p>Database:</p>
  
  <pre><code>+-------+-------------+------+
  | id    | ArticleNr   | Size | 
  +-------+-------------+------+
  | 1     | AN111       | L    | 
  | 2     | AN111       | XL   |
  | 3     | AN222       | M    |
  +-------+-------------+------+
  </code></pre>
  
  <pre class="lang-php prettyprint-override"><code>sql = "SELECT * FROM table GROUP BY article_number"
  $result = $site_db-&gt;query($sql);
  my_array = array();
  
  while ($row = $site_db-&gt;fetch_array($result)) {
      $article_number = $row['article_number'];
      $size = $row['size'];
      $my_array[${'article_number'}] .= $row['size'];
  }
  </code></pre>
  
  <p>As results I got this:</p>
  
  <blockquote>
    <p><strong>AN111</strong>: L<br>
    <strong>AN222</strong>: M</p>
  </blockquote>
  
  <p>However I want something like this: </p>
  
  <blockquote>
    <p><strong>AN111</strong>: L - XL<br>
    <strong>AN222</strong>: M</p>
  </blockquote>
  
  <p>Any help will be appreciated </p>