[Php] do not generate initilization value for extern fields (fixed issue #1628)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6542 f16182fa-f095-11de-8f43-4547254af6c6
[Php] respect error_reporting configuration (fixed issue #1625)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6543 f16182fa-f095-11de-8f43-4547254af6c6