title: How to insert values of multiple select
body: <p>I have a list multiple select, this is the code : </p>
  
  <pre><code>&lt;form method="post" action=""&gt;
        &lt;select name=thematique[] multiple&gt;
          &lt;option value="1"&gt; MIE &lt;/option&gt;
          &lt;option value="2"&gt;  Migration &lt;/option&gt;
          &lt;option value="3"&gt; Réunification familiale &lt;/option&gt;
        &lt;/select&gt;
        &lt;button type="submit" class="button" name="categoriser"&gt;Catégoriser&lt;/button&gt;
      &lt;/form&gt;
  </code></pre>
  
  <p>My problem is if I select MIE + Migration + Réunification familiale, so I have 3 lines in my data base for the same ID. 
  I want to have one line which will insert all options of the select (0 1 2 or 3).</p>
  
  <pre><code>$id_struct=$_POST['id_struct'];
  $thematique=$_POST['thematique']);
  foreach($thematique as $item) {
                  $string= $item.' ';
                  echo $string;
  
      $bdd-&gt;exec("INSERT INTO categorisation SET id_thematique=$string
                      WHERE id_struct=$id_struct");
      }
  </code></pre>
  
  <p>PS : id_thematique is a foreign key. </p>