Force recompile of cached twig files when PHP version changes

[mahagr]

Many cached PHP template files contain code that is specific to the PHP version you are using. This causes fatal errors for example in test sites, which have multiple different PHP versions installed.

Right now Twig_Cache_Filesystem has this code:

    public function generateKey($name, $className)
    {
        $hash = hash('sha256', $className);
        return $this->directory.$hash[0].$hash[1].'/'.$hash.'.php';
    }

Should something like PHP_VERSION be added to the key, maybe inside the $hash?

[mahagr]

Unfortunately $this->directory has private access, so I cannot just extend the class either.

[mahagr]

I copied the class and used the following code myself:

    public function generateKey($name, $className)
    {
        $hash = hash('sha256', $className . '-' . PHP_VERSION);
        return $this->directory.$hash[0].$hash[1].'/'.$hash.'.php';
    }

[fabpot]

Doing this with PHP_VERSION is not a good idea as people might generate the cache on PHP 5.4.3 and then deploy this on a PHP 5.4.4 production server, which would invalidate the cache for no reasons as the cache is exactly the same in this case. So, we need to only differentiate the cache when Twig actually generates a different PHP code.

See #2125

[mahagr]

Agreed, but see my comment/concern in the pull request.