在Magento中禁用PHP服务器变量的缓存

Question

I'm trying to use the data from the $_SERVER['HTTP_USER_AGENT'] php variable for some custom functionality in Magento.

However, I'm not sure if this variable is cached because it seems to act like a constant.

I'm using Chrome, and when I use two different tabs, one with mobile emulation, and one without, I see the same user agent string. When I do the same thing on a test script on my local PHP, it shows me the user agent string for the specific tab ie mobile user agent string on mobile emulator, and a desktop one otherwise.

I also tried this using two different browsers (Chrome and Firefox) and after a cache refresh, I opened Chrome using the iPhone emulator and see a iPhone user agent string, but when I open Firefox I see the same iPhone user agent string.

I'm not sure what's going on but I'm not enjoying this. Is there a way to disable caching permanently for PHP $_SERVER variables in Magento? Or is there some foolproof way of getting a non-cached user agent string? I've tried getenv but it does the same thing.

Answer 1

Out of the box, PHP won't cache the values in $_SERVER . It's far more likely your production Magento system is using some sort of output/full-page-caching that doesn't take user agent strings into account.

Answer 2

I have the same problem of setting cache expire without defining if it's public or private, but solved it by turning cache-control to private .

header("Cache-Control: private, must-revalidate");

with this, PHP will use more memory and CPU because because it's not using shared memory.

Answer 3

In magento 2 FPC is biggest problem. It will caching $_SERVER['HTTP_USER_AGENT'] variables too. i also faced this issue when i am giving support to mobile app developers.

To fix this issue, try the foll

protected $httpHeader;


public function __construct(
   ...
    \Magento\Framework\HTTP\Header $httpHeader
   ...
) {
    $this->httpHeader = $httpHeader;
}

public function getUserAgent(){
  return $this->httpHeader->getHttpUserAgent();        
}

this file Magento\\Framework\\HTTP\\Header returns clean value of user agent. so no caching problem.