fix php disambiguation regex

[smola]

Description

Because of an error in the regular expression, disambiguation rule for the .php
matched any non-empty file as PHP, except for Hack files.

Note that this means that now files with .php but containing no <? will be not classified as PHP unless other strategy kicks in. If that is not the desired behaviour, we should just remove the PHP regex and make it explicit that it is a catch-all fallback.

Checklist:

• I am fixing a misclassified language
  • I have included a new sample for the misclassified language:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

[pchaigno]

Nice catch! Thanks a lot @smola!

Do you have a sample file we could use as a test for this error?

[smola]

Not really. A real world example would involve a file with .php extension that is not PHP (or Hack) at all.

[pchaigno]

Hm, it's probably not worth it to add a new fixture file (files used for tests only, as opposed to sample files) then.

LGTM!