无法将类常量定义为二进制字符串-phpserial、Laravel、PHP

我在Laravel家庭项目中使用phpserial通过串行USB端口将灯光设置输出到DMX灯光控制器。如果我声明了一个受保护的字符串，这很好，但当我试图在类中设置常量时，这不起作用。

如何创建一个由3个二进制字节（1,0,1）组成的常量？

代码片段：

<?php
namespace App'Providers;
use Illuminate'Support'ServiceProvider;
use PhpSerial;
class SerialCommsServiceProvider extends ServiceProvider
{
    /**
     * The Serial Interface
     */
    protected $serial;
    CONST INITLIGHTS = chr(1) . chr(0) . chr(1); // THIS FAILS BUT CONST MUST BE DECLARED AT TOP SCOPE IN CLASS
    protected $initLights;
    /**
     * Create a new serial interface
     *
     */
    public function __construct()
    {
        $this->serial = new PhpSerial();
        //Get environmental config or if not available, use the default (second parameter_
        $this->serial->deviceSet(env('SERIAL_DEVICE','USB0'));
        $this->serial->confBaudRate(env('SERIAL_BAUD_RATE','9600'));
        $this->serial->confParity(env('SERIAL_PARITY','none'));
        $this->serial->confCharacterLength(env('SERIAL_CHARACTER_LENGTH',8));
        $this->serial->confStopBits(env('SERIAL_STOP_BITS',1));
        $this->serial->confFlowControl(env('SERIAL_FLOW_CONTROL','none'));
        if (env('APP_ENV') === 'production') {
            // So now we need to open it
            $this->serial->deviceOpen();
            $this->initLights = chr(1) . chr(0) . chr(1); //THIS WORKS FINE, BUT AS THE INIT STRING IS A CONSTANT...