$str vaut: test <div align="center"><p><img />allo</p></div>toi
$str2 = ereg_replace("<[^>]+>", "" , $str )
$str3 = preg_replace("/<[^>]+>/", "", $str )
$str2 vaut: test allotoi
$str3 vaut: test allotoi

javascript:a="a <a>allo</a> toi"; alert(a.replace(/<[^>]+>/g, ""));

Source: http://ca3.php.net/ereg-replace