The primary reasons for skipping PHP6 were that several books had been published on what PHP6 was supposed to be (full unicode support, for example), talks had been given and the original php 6 branch was ultimately ditched. The full list of reasons are at: <a href="https:&#x2F;&#x2F;wiki.php.net&#x2F;rfc&#x2F;php6" rel="nofollow">https:&#x2F;&#x2F;wiki.php.net&#x2F;rfc&#x2F;php6</a>