- substr: documentation ( source)
- strripos: documentation ( source)
<?php
$txt="Fatti&Storie 5 - Lorem ipsum dolor sit amet [nid:35]";
$end = strripos($txt, ']');
$start =strripos($txt, ':');
$leng = $end-$start-1;
echo $start;
echo "----";
echo $end;
echo "----";
$a=substr($txt, $start, $leng);
echo $a;