Fix PHP 8.1 compatibility issues

[ediamin]

The goal of this PR is to fix some error and warning notices when run in the PHP 8.1.

Fixes #362

[ediamin]

@schlessera I've followed the suggestion by swissspidy. But still having some tests failure related to the encoding in DocumentTest. So far I've found out that in PHP 8.1 mb_detect_encoding works differently. Please see this line in DocumentEncoding class. For the failed tests the $detectedEncoding is ISO-8859-15 except for PHP 8.1. In PHP 8.1 its value is JIS. I tried to put the ISO-8859-15 before JIS in Encoding::DETECTION_ORDER., but this new order causes problems in other tests.

Please suggest how should I proceed.

[schlessera]

Related upstream issue: https://bugs.php.net/bug.php?id=81390

It seems like the algorithm for detecting the encoding has changed in PHP 8.1. The best approach right now seems to drastically limit the list of available encodings to more closely match was PHP 8.0 and lower was doing.

In the above issue, something like this is suggested:

$encodings = ['UTF-8', 'SJIS', 'GB2312',
         'ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4',
         'ISO-8859-5', 'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9',
         'ISO-8859-10', 'ISO-8859-13', 'ISO-8859-14', 'ISO-8859-15', 'ISO-8859-16',
         'WINDOWS-1252', 'WINDOWS-1251', 'EUC-JP', 'EUC-TW', 'KOI8-R', 'BIG-5',
         'ISO-2022-KR', 'ISO-2022-JP', 'UTF-16'
];

However, this encoding order might cause regressions in PHP 8.0 and lower, so we'll have to check for that and maybe even split the encoding order here by PHP version.

[swissspidy]

If someone passes null, shouldn't PHP yell at them for it? Converting null to empty string here would hide any potential issues in consumer code.

[ediamin]

I've tested this scenario with following code snippet and found out that if we pass null as the function argument, then $value will be Null not an empty string,

<?php

function test($a, $b = '')
{
    var_dump($a);
    var_dump($b); // $b is Null for second function call.
}

test('without b');
test('with null', null);

[ediamin]

@schlessera I've updated the existing encoding order. Looks like I did some mistake when I tried to change that order before. But it is working now for all tests. FYI the suggested encoding array does not work. PHP 8.1 produces different result than its lower versions.

[schlessera]

As discussed during our meeting, this needs many more test cases covering as many different encodings as possible, to ensure we consistently have the same behavior between PHP 8.1 and PHP 8.0 and lower.

[schlessera]

@ediamin Note that the files in the src/Validator folder are being auto-generated. You'll have to adapt the source templates, not the generated files.

[ediamin]

@schlessera I've updated the code with some new test cases. As you suggested earlier, I had to use a separate order list for PHP 8.1.

[ediamin]

@schlessera I've updated the code and added the ReturnTypeWillChange in validator source files.