- substr: documentation ( source)
- strpos: documentation ( source)
- min: documentation ( source)
- str_pad: documentation ( source)
<?php
$block = '2*';
$pos = strpos($block, '*');
if ($pos !== false) {
$num = substr($block, 0, $pos);
}
$min = str_pad($num,3,'0');
$max = min(255,str_pad($num,3,'9'));
echo $min.'-'.$max;