Rather than a bug in Phirehose, this issue is informative in nature: after upgrading to PHP 5.6.8, the consuming scripts caused high CPU spikes.
Debugging the source I found these originating here (Line 443 ironically):

https://github.com/fennb/phirehose/blob/master/lib/Phirehose.php#L443

$chunk_info=trim(fgets($this->conn)); //First line is hex digits giving us the length

It's caused by a bug in PHP:

https://bugs.php.net/bug.php?id=69402 / https://bugs.php.net/bug.php?id=69428

and fixed in PHP 5.6.9RC1:

https://github.com/php/php-src/blob/php-5.6.9RC1/NEWS