Ouch, forgot my powers of two there during a weak moment - what a careless mistake. Sorry about that!
Given the low entropy I highly doubt this to be of much benefit.
========== Original ==========
From: Lauri Kenttä lauri.kentta@gmail.com
To: Benjamin Coutu ben.coutu@zeyos.com
Date: Thu, 27 Oct 2016 17:12:15 +0200
Subject: Re: [PHP-DEV] Directly embed small strings in zvals
Limiting ourselves to these common 64 characters ([a-zA-Z0-9_.]) would
allow us to effectively store (256 / 64) * 7 = 28 characters in those
available 7-bytes plus 1 byte (minus pointer tag bit) for the length.That's wrong. 256 = 28, and 64 = 26, so you get 8/6*7 = 9 chars.
Not really better than 7 chars, especially considering that all
operations on single characters would be slower than usual.