test example of keep-alive php stream (probably cannot work)

<?php

class KeepAliveStream implements \Psr\Http\Message\StreamInterface
{
    protected $doneMessage;
    protected $keepAliveMessage;
    protected $isDone = false;

    public function __construct($keepAliveMessage = '.', $doneMessage = 'Done.')
    {
        $this->doneMessage = $doneMessage;
        $this->keepAliveMessage = $keepAliveMessage;
    }

    public function __toString()
    {
        return '__toString() not supported by ' . __CLASS__;
    }

    public function close()
    {
        //nothing needed
    }

    public function detach()
    {
        return null;
    }

    public function getSize()
    {
        return null;
    }

    public function tell()
    {
        return null;
    }

    public function eof()
    {
        return $this->isDone;
    }

    public function isSeekable()
    {
        return false;
    }

    public function seek($offset, $whence = SEEK_SET)
    {
        // TODO: Implement seek() method.
    }

    public function rewind()
    {
        // TODO: Implement rewind() method.
    }

    public function isWritable()
    {
        return false;
    }

    public function write($string)
    {
        throw new \Exception('Writing not supported by ' . __CLASS__);
    }

    public function isReadable()
    {
        return true;
    }

    public function read($length)
    {
        throw new Exception('hello');

        return $this->isDone ? $this->doneMessage : $this->keepAliveMessage;
    }

    public function getContents()
    {
        return '__getContents() not supported by ' . __CLASS__;
    }

    public function getMetadata($key = null)
    {
        return null;
    }
}