Log formatters shouldn't override referenced values

[youngguns-nl]

When you use multiple writers with different formatters, the formatter of the next writer gets the formatted event from the first writer (and so on). The reason this happens is, of course, references.

In my opinion the formatters shouldn't actually change the original values, but just return a formatted "local" version of the event. If you guys agree I can create a PR for this, but first want to discuss the possible solutions here. So any thoughts?

[youngguns-nl]

After some more debugging, forget about the different writers and formatters, even with one writer and formatter things get messed up :-)

$logger = new Zend\Log\Logger();
Zend\Log\Logger::registerErrorHandler($logger);
$streamWriter = new Zend\Log\Writer\Stream('/tmp/test.log');
$streamWriter->setFormatter(new Zend\Log\Formatter\Simple());

$logger->addWriter($streamWriter);

$testArray = array(
    'foo' => 'testing',
    'bar' => array(
        'lorum' => array(
            'ipsum',
            'dolar sit',
        )
    )
);

var_dump(gettype($testArray)); //output: string 'array' (length=5)
trigger_error('foobar');
var_dump(gettype($testArray)); //output: string 'string' (length=6)

So somehow the test array is converted into an json encoded string.

[marc-mabe]

Interesting, your example results in an infinite loop using the current master branch

[gws]

This looks related to #4503 as well.