According to This Announcement on 7.5.8:
Compatibility with PHP 5.4 and PHP 5.5
Compatibility with MySQL 5.6

There are several references posted in that category referencing v7.6 (as far back as December 2012), I'd hope that if we recieve a future build that it'd be tested against newer builds of both PHP and MySQL; but the supposed development postings said we'd at least be beta'ing something by now after nearly two years of development.

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