Remove spaces and comments from PHP code.

Operations:

• remove unnecessary whitespace, change necessary whitespace to \n
• strip comments, preserve only the first doc-comment
• minify variables, e.g. in function f($long) { return $long; } (incompatible with $GLOBALS and named arguments)
• remove extra {}, e.g. in if (true) { oneCommand(); }
• remove ?><?php and empty <?php ?>
• change ?>HTML<?php to echo 'HTML'
• join consecutive echo, e.g. in echo 'a'; echo 'b';
• strip public visibility or change it to var

Demo: https://vrana.github.io/PhpShrink/

The main user is Adminer.