Comment processing behavior when using line breaks in PHP

[Steven]

Hello,

I'd like to clarify if there may be a bug (or feature) when processing 
translator comments within PHP code that contains a line break (Unix style - 
LF) before the first function argument (which is valid PHP syntax).

For example, given the following PHP file (Filename: test.php, Unix line 
breaks, UTF-8 encoding):

  <?php
  /// TRANSLATORS: Test comment
  _(
  'Test');

If we run the following command (using Windows 10):

  .\xgettext.exe -L PHP --add-comments=TRANSLATORS: test.php

...the resulting messages.po output file is missing the translator comment:

  #: test.php:5
  msgid "Test"
  msgstr ""

However, if we modify the PHP file (test.php) to the following:

  <?php
  /// TRANSLATORS: Test comment
  _(''.
  'Test');

...and run the same xgettext command, the resulting messages.po output file now 
contains the comment:

  #. TRANSLATORS: Test comment
  #: test.php:4
  msgid "Test"
  msgstr ""

We expected the comment to appear in the first messages.po file, given the 
first PHP file uses valid PHP syntax.

Many thanks for your advice.