PHP检测GIF图片是否为动画还是静止

//检测图片是否为GIF动画
function CheckAnimation($image_file){
$arr_hz=explode('.',$image_file);
$img_name=$arr_hz[count($arr_hz)-1];
if(strtolower($img_name)=='gif' && FileExists($image_file)){
$fp = fopen($image_file, 'rb');
$image_head = fread($fp,1024);
fclose($fp);
return preg_match("/".chr(0x21).chr(0xff).chr(0x0b).'NETSCAPE2.0'."/",$image_head)  ? true : false;
}else{
return false;
}
}