src/Generator/OpenSSLGenerator.php
public static function isSupported()
    {
        $supported = false;
        if (function_exists('openssl_random_pseudo_bytes')) {
            if (version_compare(PHP_VERSION, '5.3.7') >= 0 || (PHP_OS & "\xDF\xDF\xDF") !== 'WIN') {
                $supported = true;
            }
        }

        return $supported;
    }
public static function isSupported()
    {
        $supported = false;
        if (function_exists('openssl_random_pseudo_bytes')) {
            if (version_compare(PHP_VERSION, '5.3.7') >= 0 || (PHP_OS & "\xDF\xDF\xDF") !== 'WIN') {
                $supported = true;
            }
        }

        return $supported;
    }
Test system support for this generator.

PHP versions prior to 5.3.7 have a bug in the Windows implementation of
this generator. The implementation used OpenSSL functions which could
cause blocking for an indefinite period of time on headless
non-interactive Windows servers. Because of this, the generator is not
supported for PHP versions < 5.3.7 on Windows.

The OpenSSL function this generator uses simply wraps Microsoft's
CryptoAPI on PHP versions >= 5.4.0 on Windows. It should be noted that
this is also exactly how the MCrypt generator operates on Windows.

@return boolean Returns true if the generator is supported on the current
platform, otherwise false.