Really can't understand why but if I do this:
$birra = isset( $passaggio['et2018-nome_birra'] ) ? $passaggio['et2018-nome_birra'] : '<a href="'.get_the_permalink().'" title="'.get_the_title().'"><p>Birra: '.$birra.'</p></a>';
it doesn't work.
If I do like this, instead:
if (isset($passaggio['et2018-nome_birra'])){
$birra = $passaggio['et2018-nome_birra'];
}
echo '<a href="'.get_the_permalink().'" title="'.get_the_title().'"><p>Birra: '.$birra.'</p></a>';
It works.