title: What is this bitwise OR doing in this weird array key construct?
body: <p>Can someone explain to me what this means?? I have never seen this construct - taken from the <a href="http://doc.prestashop.com/display/PS14/Creating+a+PrestaShop+module#CreatingaPrestaShopmodule-Creatingthemodule%27sbackofficetab%2Canditsclass">Prestashop doc</a></p>
  
  <pre><code>foreach ( $languages as $language )
  {
    echo '&lt;div id="test_' . $language['id_lang'|'id_lang'] .... // &lt;-- What the??
    // ... 
  }
  </code></pre>
  
  <p>$language contains the following keys:</p>
  
  <pre><code>Array
  (
      [id_lang] =&gt; 1
      [name] =&gt; English (English)
      // and others... 
  )
  </code></pre>
  
  <p>The result is that it takes the value of $language["id_lang"] - 1. But I don't understand the syntax and can't find any documentation about it.</p>