IPv4 network packet: PHP parsing library

<?php
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

namespace {
    class Ipv4Packet extends \Kaitai\Struct\Struct {
        public function __construct(\Kaitai\Struct\Stream $_io, \Kaitai\Struct\Struct $_parent = null, \Ipv4Packet $_root = null) {
            parent::__construct($_io, $_parent, $_root);
            $this->_read();
        }

        private function _read() {
            $this->_m_b1 = $this->_io->readU1();
            $this->_m_b2 = $this->_io->readU1();
            $this->_m_totalLength = $this->_io->readU2be();
            $this->_m_identification = $this->_io->readU2be();
            $this->_m_b67 = $this->_io->readU2be();
            $this->_m_ttl = $this->_io->readU1();
            $this->_m_protocol = $this->_io->readU1();
            $this->_m_headerChecksum = $this->_io->readU2be();
            $this->_m_srcIpAddr = $this->_io->readBytes(4);
            $this->_m_dstIpAddr = $this->_io->readBytes(4);
            $this->_m__raw_options = $this->_io->readBytes(($this->ihlBytes() - 20));
            $_io__raw_options = new \Kaitai\Struct\Stream($this->_m__raw_options);
            $this->_m_options = new \Ipv4Packet\Ipv4Options($_io__raw_options, $this, $this->_root);
            $this->_m__raw_body = $this->_io->readBytes(($this->totalLength() - $this->ihlBytes()));
            $_io__raw_body = new \Kaitai\Struct\Stream($this->_m__raw_body);
            $this->_m_body = new \ProtocolBody($this->protocol(), $_io__raw_body);
        }
        protected $_m_version;
        public function version() {
            if ($this->_m_version !== null)
                return $this->_m_version;
            $this->_m_version = (($this->b1() & 240) >> 4);
            return $this->_m_version;
        }
        protected $_m_ihl;
        public function ihl() {
            if ($this->_m_ihl !== null)
                return $this->_m_ihl;
            $this->_m_ihl = ($this->b1() & 15);
            return $this->_m_ihl;
        }
        protected $_m_ihlBytes;
        public function ihlBytes() {
            if ($this->_m_ihlBytes !== null)
                return $this->_m_ihlBytes;
            $this->_m_ihlBytes = ($this->ihl() * 4);
            return $this->_m_ihlBytes;
        }
        protected $_m_b1;
        protected $_m_b2;
        protected $_m_totalLength;
        protected $_m_identification;
        protected $_m_b67;
        protected $_m_ttl;
        protected $_m_protocol;
        protected $_m_headerChecksum;
        protected $_m_srcIpAddr;
        protected $_m_dstIpAddr;
        protected $_m_options;
        protected $_m_body;
        protected $_m__raw_options;
        protected $_m__raw_body;
        public function b1() { return $this->_m_b1; }
        public function b2() { return $this->_m_b2; }
        public function totalLength() { return $this->_m_totalLength; }
        public function identification() { return $this->_m_identification; }
        public function b67() { return $this->_m_b67; }
        public function ttl() { return $this->_m_ttl; }
        public function protocol() { return $this->_m_protocol; }
        public function headerChecksum() { return $this->_m_headerChecksum; }
        public function srcIpAddr() { return $this->_m_srcIpAddr; }
        public function dstIpAddr() { return $this->_m_dstIpAddr; }
        public function options() { return $this->_m_options; }
        public function body() { return $this->_m_body; }
        public function _raw_options() { return $this->_m__raw_options; }
        public function _raw_body() { return $this->_m__raw_body; }
    }
}

namespace Ipv4Packet {
    class Ipv4Options extends \Kaitai\Struct\Struct {
        public function __construct(\Kaitai\Struct\Stream $_io, \Ipv4Packet $_parent = null, \Ipv4Packet $_root = null) {
            parent::__construct($_io, $_parent, $_root);
            $this->_read();
        }

        private function _read() {
            $this->_m_entries = [];
            $i = 0;
            while (!$this->_io->isEof()) {
                $this->_m_entries[] = new \Ipv4Packet\Ipv4Option($this->_io, $this, $this->_root);
                $i++;
            }
        }
        protected $_m_entries;
        public function entries() { return $this->_m_entries; }
    }
}

namespace Ipv4Packet {
    class Ipv4Option extends \Kaitai\Struct\Struct {
        public function __construct(\Kaitai\Struct\Stream $_io, \Ipv4Packet\Ipv4Options $_parent = null, \Ipv4Packet $_root = null) {
            parent::__construct($_io, $_parent, $_root);
            $this->_read();
        }

        private function _read() {
            $this->_m_b1 = $this->_io->readU1();
            $this->_m_len = $this->_io->readU1();
            $this->_m_body = $this->_io->readBytes(($this->len() > 2 ? ($this->len() - 2) : 0));
        }
        protected $_m_copy;
        public function copy() {
            if ($this->_m_copy !== null)
                return $this->_m_copy;
            $this->_m_copy = (($this->b1() & 128) >> 7);
            return $this->_m_copy;
        }
        protected $_m_optClass;
        public function optClass() {
            if ($this->_m_optClass !== null)
                return $this->_m_optClass;
            $this->_m_optClass = (($this->b1() & 96) >> 5);
            return $this->_m_optClass;
        }
        protected $_m_number;
        public function number() {
            if ($this->_m_number !== null)
                return $this->_m_number;
            $this->_m_number = ($this->b1() & 31);
            return $this->_m_number;
        }
        protected $_m_b1;
        protected $_m_len;
        protected $_m_body;
        public function b1() { return $this->_m_b1; }
        public function len() { return $this->_m_len; }
        public function body() { return $this->_m_body; }
    }
}