$nasapage = file_get_contents("http://marsoweb.nas.nasa.gov/HiRISE/hirise_images/mapped/");
//ereg('href="([[:alnum:]_/]{10,16})"',$nasapage,$regs);
$preg =
"/a[\s]+[^>]*?href[\s]?=[\s\"\']+(.{16})[\"\']+.*?>"
."([^<]+|.*?)?<\/a>/";
preg_match_all($preg,$nasapage,$regs);
echo '';
?>