As Matthew Weier O'Phinney mentions in his latest post, the PSR-7 standard (HTTP) has passed and is officially accepted as a standard by the PHP-FIG group.
The road to PSR-7 was a long and winding one. It started in summer of 2012 as a draft proposal on HTTP clients by Benjamin Eberlei, during which others proposed that perhaps a smaller standard on the HTTP message interfaces themselves - which would also allow targeting server-side applications, as those rely on the messages.
He follows the proposal's flow through the PHP-FIG process, pointing out several others who contributed along the way and what changed along the way. He also includes a section of thanks for some of the other developers and PHP-FIG members that made contributions along the way.