Since PHP 7 is shiny and new, it unsurprisingly got a lot of coverage. If you’re migrating from PHP 5, or considering doing so, this talk will let you know what to expect. It also gives some brief information on the grace periods which have been extended to the 5 branch, including specifics on PHP 5.5 and PHP 5.6.
https://www.w3.org/WAI/gettingstarted/tips/