jonnnnyw/php-phantomjs — pull request #14 by nbrogi (2014-05-04 15:22:19+00:00)
Title: Added way to set viewport width/height

I don't know if you could already do this and it was simply missing from the README, but now you can specify the width/height of the viewport for screenshots:
$request->setViewportWidth(1024);
$request->setViewportHeight(768);