function chkurl($url){
    $handle = curl_init($url);
    curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);
    curl_setopt($handle, CURLOPT_CONNECTTIMEOUT, 10);//设置超时时间
    curl_exec($handle);
    //检查是否404（网页找不到）
    $httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
    if($httpCode == 404) {
      return false;
    }else{
        return true;
    }
    curl_close($handle);

 }