function is_cloudflare_ip($ip) { // updated: 2025-04-04  
  // Convert IP string to number
  if (is_string($ip)) {
    $bytes = explode('.', $ip);
    $ip = 0;
    foreach ($bytes as $n) {
      $ip <<= 8;
      $ip |= (int)$n;
    }
  }
  // Check rules
  switch ($ip & 0b0_11111111_11111000_00000000_00000000) { // mask: 255.248.0.0
    case        0b0_01101000_00010000_00000000_00000000:   // ip:   104.16.0.0
    case        0b0_10101100_01000000_00000000_00000000:   // ip:   172.64.0.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111100_00000000_00000000) { // mask: 255.252.0.0
    case        0b0_01101000_00011000_00000000_00000000:   // ip:   104.24.0.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111110_00000000_00000000) { // mask: 255.254.0.0
    case        0b0_10100010_10011110_00000000_00000000:   // ip:   162.158.0.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_10000000_00000000) { // mask: 255.255.128.0
    case        0b0_11000110_00101001_10000000_00000000:   // ip:   198.41.128.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11000000_00000000) { // mask: 255.255.192.0
    case        0b0_01101100_10100010_11000000_00000000:   // ip:   108.162.192.0
    case        0b0_10001101_01100101_01000000_00000000:   // ip:   141.101.64.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11110000_00000000) { // mask: 255.255.240.0
    case        0b0_10101101_11110101_00110000_00000000:   // ip:   173.245.48.0
    case        0b0_10111100_01110010_01100000_00000000:   // ip:   188.114.96.0
    case        0b0_10111110_01011101_11110000_00000000:   // ip:   190.93.240.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11111100_00000000) { // mask: 255.255.252.0
    case        0b0_01100111_00010101_11110100_00000000:   // ip:   103.21.244.0
    case        0b0_01100111_00010110_11001000_00000000:   // ip:   103.22.200.0
    case        0b0_01100111_00011111_00000100_00000000:   // ip:   103.31.4.0
    case        0b0_10000011_00000000_01001000_00000000:   // ip:   131.0.72.0
    case        0b0_11000101_11101010_11110000_00000000:   // ip:   197.234.240.0
      return true;
  }
  return false;
}