PHP regular method to filter pictures in articles

$txt="Programmer's Home_bbs.it-home.org";
$pattern='//';
$str="Replace with blank";
$txt =preg_replace($pattern,$str,$txt);
$str = preg_replace('~~s','',$str) ; //$str is the content of the article to be filtered.
?>

The above is the content of this php tutorial, once again feel the powerful power of php regularity.