png, gif, jpg 이미지 확인 방법

$fp = fopen($_FILES["thumbnail"]["tmp_name"], "r");

$image_stream = fread($fp, 64);

if ( preg_match( '/^\x89PNG\x0d\x0a\x1a\x0a/', $image_stream) )  {

    $type = "png";

} elseif ( preg_match( '/^GIF8[79]a/', $image_stream) )  {

    $type = "gif";

} elseif ( preg_match( '/^\xff\xd8/', $image_stream) )  {

    $type = "jpg";

}

fclose($fp);