Fix for HHVm issue with stream_get_meta_data

[martinssipenko]

This should fix issue when HHVM is used, since HHVM has different implemenation of tmpfile() facebook/hhvm#2336 that leads to returning empty uri key when stream_get_meta_data is used.

Warning: Filename cannot be empty in vendor/squizlabs/php_codesniffer/CodeSniffer/Reporting.php on line 237

array(10) {
  ["wrapper_type"]=>
  string(9) "plainfile"
  ["stream_type"]=>
  string(5) "STDIO"
  ["mode"]=>
  string(0) ""
  ["unread_bytes"]=>
  int(0)
  ["seekable"]=>
  bool(true)
  ["uri"]=>
  string(0) ""
  ["timed_out"]=>
  bool(false)
  ["blocked"]=>
  bool(true)
  ["eof"]=>
  bool(false)
  ["wrapper_data"]=>
  NULL
}

[goatherd]

👍

[gsherwood]

Thanks for this fix. I didn't originally use sys_get_temp_dir() because it isn't available in my min PHP version, but I didn't realise it caused a HHVM issue. So instead, I've just put an extra function_exists() check in.