- var_dump: documentation ( source)
- preg_match_all: documentation ( source)
<?php
$string = "<h2>Title of post</h2> 1 category <strong>task 1</strong> 1 category <strong>task 2</strong> 1 category <strong>task 3</strong> ";
$zz = preg_match_all('#<strong>(.*?)</strong>#',$string,$matches);
echo var_dump($zz);