Apply suggestions from code review

Co-authored-by: Jakob Lykke Andersen <jakobandersen@users.noreply.github.com>

doc/tutorial/describing-code.rst

@@ -240,11 +240,13 @@ Documenting and cross-referencing objects
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Sphinx also supports documenting and cross-referencing objects written in
-other programming languages. There are four extra built-in domains:
-C, C++, JavaScript, and reStructuredText, and third party extensions may
+other programming languages. There are four additional built-in domains:
+C, C++, JavaScript, and reStructuredText. Third-party extensions may
 define domains for more languages, such as
-`Fortran <https://sphinx-fortran.readthedocs.io>`_
-or `Julia <http://bastikr.github.io/sphinx-julia>`_.
+
+- `Fortran <https://sphinx-fortran.readthedocs.io>`_,
+- `Julia <http://bastikr.github.io/sphinx-julia>`_, or
+- `PHP <https://github.com/markstory/sphinxcontrib-phpdomain>`_.
 
 For example, to document a C++ type definition, you would use the built-in
 :rst:dir:`cpp:type` directive, as follows: