header flushing code from zend-diactoros

header-flush.php.text

array_walk($headers, function ($value, $key) {

  # validate header key (ref: zend-diactoros)
  if (! preg_match('/^[a-zA-Z0-9\'`#$%&*+.^_|~!-]+$/', $key)) {
    throw new InvalidArgumentException("Invalid header name - {$key}");
  }

  # validate header values (ref: zend-diactoros)
  $values = is_array($value) ? $value : [$value];
  foreach ($values as $val) {
    if (
      preg_match("#(?:(?:(?<!\r)\n)|(?:\r(?!\n))|(?:\r\n(?![ \t])))#", $val) ||
      preg_match('/[^\x09\x0a\x0d\x20-\x7E\x80-\xFE]/', $val)
    ) {
      throw new InvalidArgumentException("Invalid header value - {$val}");
    }
  }

  header($key.': '.implode(',', $values));
});