Code:
$row2['url'] = $_site_www2.'/folder/'.str_replace('1XXX1_', '', $row2['2_folder']).'-name.ext';
or if the string you want to remove is always same length but different numbers... i.e. "1XYZ1_"...
Code:
$row2['url'] = $_site_www2.'/folder/'.substr($row2['2_folder'], 6).'-name.ext';