JSON can contain null as a value. Therefore, I do not know if this way of solving the problem is correct.

If the user input is 'null', json_decode() returns null.
null is not an array, so there is no value for a key $index.

i mean

// body: {"var" : null}
$request->getVar('var'); // null

// body: {}
$request->getVar('var'); // null

// body: null
$request->getVar('var'); // null

If we assume that the value "var" can be null, then the last two examples are incorrect behavior.
And it seems to me you need to throw an exception.

If we compare it with working with an array, then:

$a = [];
$a['test'];
// Warning:  Undefined array key "test"

$a = null;
$a['test'];
// Warning:  Trying to access array offset on value of type null

It depends on getJsonVar()'s specification.
It throws an exception or not.

If it should throw an exception, #5391 is not a bug.

@kenjis could you verify PHPUnit error on develop branch?

@samsonasik Do you mean this?

PHP Fatal error: Declaration of PhpCoveralls\Bundle\CoverallsBundle\Console\Application::getDefinition() must be compatible with Symfony\Component\Console\Application::getDefinition(): Symfony\Component\Console\Input\InputDefinition in /home/runner/.composer/vendor/php-coveralls/php-coveralls/src/Bundle/CoverallsBundle/Console/Application.php on line 44
https://github.com/codeigniter4/CodeIgniter4/runs/4376649089?check_suite_focus=true

It is an error of PhpCoveralls: php-coveralls/php-coveralls#327

Yes, is there a way to pin to specific coveralls version that is working?

Adding this to composer.json?

"symfony/console": "< 6.0",

Yes, that's probably the temporary fix 👍

@samsonasik Okay, I will do it.