Update PHP nightly

I am seeing that you guys are using a build from the 5th of August right now.
It would be nice if this could be updated, since the 5th of August, the
signature of zend_update_property_* has changed from taking a zval to zend_object.
This can cause crashes for extensions that already adapted this.

So it seems the current nightly build fails because it can’t find:
sed: can’t read /home/travis/.php-build/share/php-build/definitions/master: No such file or directory

Seems it fails due to this: https://github.com/php-build/php-build/commit/03c6251b00288cf7531a2daabe4dab86c457a0a5

Definition for 8.0snapshot was added and a PR to utilize it:

A related issue has been reported that is causing this:

nightly is not pre-installed; installing
Downloading archive: https://storage.googleapis.com/travis-ci-language-archives/php/binaries/ubuntu/16.04/x86_64/php-nightly.tar.bz2
$ curl -sSf --retry 5 -o archive.tar.bz2 $archive_url && tar xjf archive.tar.bz2 --directory /
$ phpenv global nightly
rbenv: version `nightly' not installed

The command "phpenv global nightly" failed and exited with 1 during .

Another PR has been created to fix this:

Images seem to be up to date now :tada: