Fix #225 - compatibility with PHP 8.4

[fisharebest]

Q	A
Branch?	master
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes (except an unrelated test which fails in the existing code)
Fixed tickets	#255
License	MIT

This fix contains two changes for compatibility with PHP 8.4

• Implicit null function parameters changed to explicit null. e.g. (Foo $foo = null) becomes (?Foo $foo = null)`
• Add new property to CommonParser, prevent "cannot create dynamic properties"

It also updates the test script to include recent versions of PHP.

[fisharebest]

This PR supercedes #215