Get access_token with PHP

$url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=".AppID."&secret=".AppSecret;
$result = http_request($url);
//Generate file, save token
$dir = __DIR__; //The real path, the php execution of the crontab command is in cli mode, the relative path cannot be recognized correctly, so use __DIR__
$filename = $dir."/access_token.php";
create_file($filename, $result);
function http_request($url,$data = null){
  $curl = curl_init();
  curl_setopt($curl, CURLOPT_URL, $url);
  curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
  curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, FALSE);
  if (!empty($data)){
    curl_setopt($curl, CURLOPT_POST, 1);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
  }
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
  $output = curl_exec($curl);
  curl_close($curl);
  return $output;
}
//generate file
function create_file($filename, $content){
  $fp = fopen($filename, "w");
  fwrite($fp, "" . $content);
  fclose($fp);
}