Compatibility with PHP 8.0

[eclipxe13]

PHPUnit is upgraded since this library supports PHP >= 7.2 and PHPUnit 8 supports from 7.2 until 8.0

• Fix XSLTProcessor::transformToDoc signature to match with PHP XSLTProcessor.
• Fix Math functions by casting to floats.
• Update tests to work with PHPUnit 8.
• Travis-CI: Fixed compatibility with XDebug 3.0.
• Travis-CI: Due compatibility issues with PHP 8.0, do not install or test php-cs-fixer and phpstan.

Important: One pending task (that requires a different PR) is to upgrade PHPStan from version 0.11 to version 0.12.

[frederikbosch]

Nice! We could drop 7.2 and only support 7.3/7.4/8.0 now. What do you think?

[eclipxe13]

It's up to you, PHP 7.2 has reached EOL since 2020-11-30.
If PHP 7.2 is drop then we can upgrade PHPUnit to version 9.

[frederikbosch]

Let's go for PHP7.3+ only. I rather not support version that reached EOL.

[eclipxe13]

Just try to make it work upgrading to PHPUnit 9, there are two files that require to change on the test suite:

• assertRegExp is deprecated, substitute with assertMatchesRegularExpression
• expectException(Error::class) should be replaced with expectError(), also expectExceptionMessage() replace to expectErrorMessage()

The main issue I see on upgrade to PHPUnit 9 is that it has incompatible dependencies with PHPStan 0.11.
Also PHPStan 0.11 has been deprecated since 2019-10-22,

So, I would recommend to you follow the path:

1. Merge this PR that allows this library to run using PHP 8.0
2. Upgrade to PHPStan 0.12 and solve the all the issues (this is not trivial, level 6 is tedious)
3. Upgrade to PHPUnit 9 and PHP >= 7.3

PHPStan 0.12 counts 175 errors on max level:

• Level 2: 3 trivial errors
• Level 4: +8 errors, trivial but requires your review
• Level 6: +91 errors, need a lot of annotations on traversables and arrays
• Level 7: +8 errors
• Level 8: +65 errors

I can work with you on this process, what is your opinion?

[frederikbosch]

Let's include the drop of PHP 7.2 in this PR by just removing it from the testsuite. Then I'll merge. I agree with you on the rest of path.

[frederikbosch]

I can do the PHPStan upgrade to 0.12 no problem. I have done it before for my mail package. Mostly it is improving docblocks with generics syntax.

[frederikbosch]

Fantastic, great work!

[vkondratjevs]

You can crate tag to php8 ?

[frederikbosch]

Yes, done!