In last week's RFC meeting, it was proposed that we require PHP 5.5 for MediaWiki core git master (to be 1.27.0), and this was approved without objections.
After the meeting, Mark Clements (HappyDog), a long-term valued contributor to the project, expressed strenuous objections to this decision on the ticket: https://phabricator.wikimedia.org/T118932
On the ticket, I proposed a process whereby the RFC will be reopened for review if any existing Phabricator user will second the motion. If you do object, please register your objection on Phabricator.
In the meantime, please do not merge any changes which require PHP 5.4+.
-- Tim Starling