The `Util\Standards::getInstalledStandardPath()` method returns either a string or `null`, however the `strpos()` method which is used in both the `Util\Common::isPharFile()` method, as well as in the follow-on condition, only accepts a `string` as `$haystack`.

As of PHP 8.1, this will generated a deprecation notice `strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated`.

Discovered by testing an external standard against PHPCS `master` on PHP 8.1.

Fixed now.

The `Util\Standards::getInstalledStandardPath()` method returns either a string or `null`, however the `strpos()` method which is used in both the `Util\Common::isPharFile()` method, as well as in the follow-on condition, only accepts a `string` as `$haystack`.

As of PHP 8.1, this will generate a deprecation notice `strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated`.

Discovered while testing an external standard against PHPCS `master` on PHP 8.1.

Fixed now.

The `Util\Standards::getInstalledStandardPath()` method returns either a string or `null`, however the `strpos()` method which is used in both the `Util\Common::isPharFile()` method, as well as in the follow-on condition, only accepts a `string` as `$haystack`.

As of PHP 8.1, this will generate a deprecation notice `strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated`.

Discovered while testing an external standard against PHPCS `master` on PHP 8.1.

Fixed now.

On PHP 8.1, passing `null` to `strtolower()` generates a `strtolower(): Passing null to parameter #1 ($string) of type string is deprecated` notice.

The `File::getDeclarationName()` will return `null` for anonymous classes, so we need an extra safeguard here.

This fix is covered by the existing unit tests and was exposed when running the tests on PHP 8.1 with `error_reporting` set to `E_ALL`.

On PHP 8.1, passing `null` to `strtolower()` generates a `strtolower(): Passing null to parameter #1 ($string) of type string is deprecated` notice.

The `File::getDeclarationName()` will return `null` for anonymous classes, so we need an extra safeguard here.

This fix is covered by the existing unit tests and was exposed when running the tests on PHP 8.1 with `error_reporting` set to `E_ALL`.

…-home

Update for Composer name + docs for new repo home

This adds another set of dedicated tests to safeguard how XML docs which don't follow the specification are handled.

This initial set of tests for this documents the current behaviour [*]. This behaviour may not always be the desired behaviour, in which case, this will be fixed in follow-up commits.

To get these tests up and running, the following fatal errors needed to be fixed:

* Fatal error when a code comparison only contains a single code element:
    ```
    Fatal error: Uncaught Error: Call to a member function getAttribute() on null in path/to/PHP_CodeSniffer/src/Generators/Markdown.php:253
    Stack trace:
    #0 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(139): PHP_CodeSniffer\Generators\Markdown->getFormattedCodeComparisonBlock(Object(DOMElement))
    #1 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(39): PHP_CodeSniffer\Generators\Markdown->processSniff(Object(DOMElement))
    squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(99): PHP_CodeSniffer\Generators\Markdown->generate()
    squizlabs#3 path/to/PHP_CodeSniffer/bin/phpcs(14): PHP_CodeSniffer\Runner->runPHPCS()
    squizlabs#4 {main}
      thrown in path/to/PHP_CodeSniffer/src/Generators/Markdown.php on line 253
    ```

* Fatal error when a code element contains no textual content:
    ```
    Fatal error: Uncaught Error: Call to a member function getAttribute() on null in path/to/PHP_CodeSniffer/src/Generators/Markdown.php:246
    Stack trace:
    #0 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(139): PHP_CodeSniffer\Generators\Markdown->getFormattedCodeComparisonBlock(Object(DOMElement))
    #1 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(39): PHP_CodeSniffer\Generators\Markdown->processSniff(Object(DOMElement))
    squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(99): PHP_CodeSniffer\Generators\Markdown->generate()
    squizlabs#3 path/to/PHP_CodeSniffer/bin/phpcs(14): PHP_CodeSniffer\Runner->runPHPCS()
    squizlabs#4 {main}
      thrown in path/to/PHP_CodeSniffer/src/Generators/Markdown.php on line 246
    ```

Both of these fatals are fixed by adding defensive coding validating that there are (at least) two code blocks to the `getFormattedCodeComparisonBlock()` methods for all three generator classes.

This adds another set of dedicated tests to safeguard how XML docs which don't follow the specification are handled.

This initial set of tests for this documents the current behaviour [*]. This behaviour may not always be the desired behaviour, in which case, this will be fixed in follow-up commits.

To get these tests up and running, the following fatal errors needed to be fixed:

* Fatal error when a code comparison only contains a single code element:
    ```
    Fatal error: Uncaught Error: Call to a member function getAttribute() on null in path/to/PHP_CodeSniffer/src/Generators/Markdown.php:253
    Stack trace:
    #0 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(139): PHP_CodeSniffer\Generators\Markdown->getFormattedCodeComparisonBlock(Object(DOMElement))
    #1 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(39): PHP_CodeSniffer\Generators\Markdown->processSniff(Object(DOMElement))
    squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(99): PHP_CodeSniffer\Generators\Markdown->generate()
    squizlabs#3 path/to/PHP_CodeSniffer/bin/phpcs(14): PHP_CodeSniffer\Runner->runPHPCS()
    squizlabs#4 {main}
      thrown in path/to/PHP_CodeSniffer/src/Generators/Markdown.php on line 253
    ```

* Fatal error when a code element contains no textual content:
    ```
    Fatal error: Uncaught Error: Call to a member function getAttribute() on null in path/to/PHP_CodeSniffer/src/Generators/Markdown.php:246
    Stack trace:
    #0 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(139): PHP_CodeSniffer\Generators\Markdown->getFormattedCodeComparisonBlock(Object(DOMElement))
    #1 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(39): PHP_CodeSniffer\Generators\Markdown->processSniff(Object(DOMElement))
    squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(99): PHP_CodeSniffer\Generators\Markdown->generate()
    squizlabs#3 path/to/PHP_CodeSniffer/bin/phpcs(14): PHP_CodeSniffer\Runner->runPHPCS()
    squizlabs#4 {main}
      thrown in path/to/PHP_CodeSniffer/src/Generators/Markdown.php on line 246
    ```

Both of these fatals are fixed by adding defensive coding validating that there are (at least) two code blocks to the `getFormattedCodeComparisonBlock()` methods for all three generator classes.

This sniff could throw the following fatal errors when it encountered parse errors/during live coding:

```
Fatal error: Uncaught PHP_CodeSniffer\Exceptions\RuntimeException: strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in path/to/PHPCS/src/Standards/Generic/Sniffs/NamingConventions/ConstructorNameSniff.php on line 83 in path/to/PHPCS/src/Runner.php on line 624

Fatal error: Uncaught PHP_CodeSniffer\Exceptions\RuntimeException: strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in path/to/PHPCS/src/Standards/Generic/Sniffs/NamingConventions/ConstructorNameSniff.php on line 167 in path/to/PHPCS/src/Runner.php on line 624
```

Fixed now by adding more defensive coding.

Includes test safeguarding the fix.

…report

Okay, so this is an awkward one.

If both the `Code` + the `Diff` report were requested + caching was turned on + the _order_ of the requested reports was `Code,Diff` (i.e. first the code report), the following fatal error which would occur:
```
Fatal error: Uncaught Error: Call to a member function getFixableCount() on null in path/to/PHP_CodeSniffer/src/Fixer.php:144
Stack trace:
#0 path/to/PHP_CodeSniffer/src/Reports/Diff.php(73): PHP_CodeSniffer\Fixer->fixFile()
#1 path/to/PHP_CodeSniffer/src/Reporter.php(285): PHP_CodeSniffer\Reports\Diff->generateFileReport(Array, Object(PHP_CodeSniffer\Files\LocalFile), true, 150)
squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(659): PHP_CodeSniffer\Reporter->cacheFileReport(Object(PHP_CodeSniffer\Files\LocalFile))
squizlabs#3 path/to/PHP_CodeSniffer/src/Runner.php(400): PHP_CodeSniffer\Runner->processFile(Object(PHP_CodeSniffer\Files\LocalFile))
squizlabs#4 path/to/PHP_CodeSniffer/src/Runner.php(119): PHP_CodeSniffer\Runner->run()
squizlabs#5 path/to/PHP_CodeSniffer/bin/phpcs(30): PHP_CodeSniffer\Runner->runPHPCS()
squizlabs#6 {main}
  thrown in path/to/PHP_CodeSniffer/src/Fixer.php on line 144
```

To reproduce the issue (on `master`):
1. Create a small test file like:
    ```php
    <?php

    echo 'hello'.callMe( $p );
    ```
2. Run the following command to initialize the cache:
    ```bash
    phpcs -ps ./test.php --standard=PSR2 --report=Code,Diff --cache
    ```
    All should be fine.
3. Now run the same command again and see the fatal error.

Some investigating later, it turns out that both the `Code` report, as well as the `Diff` report, re-parse the current file, with the `Diff` report initializing the fixer once the file has reparsed, but the `Code` report not doing so (as it doesn't need the fixer).
The problem with that is that the `Code` report basically leaves the `Fixer` in an invalid state, leading to the above error.

While it is up for debate whether reports should ever (be allowed to) re-parse files, for now, let's fix the fatal.

Re-evaluating the report setup should definitely be done, but should probably wait until the Reports classes have test coverage.