Make any PHP Exception serializable by flattening complex values in backtrace.

flattenExceptionBacktrace.php

<?php
    function flattenExceptionBacktrace(\Exception $exception) {
        $traceProperty = (new \ReflectionClass('Exception'))->getProperty('trace');
        $traceProperty->setAccessible(true);

        $flatten = function(&$value, $key) {
            if ($value instanceof \Closure) {
                $closureReflection = new \ReflectionFunction($value);
                $value = sprintf(
                    '(Closure at %s:%s)',
                    $closureReflection->getFileName(),
                    $closureReflection->getStartLine()
                );
            } elseif (is_object($value)) {
                $value = sprintf('object(%s)', get_class($value));
            } elseif (is_resource($value)) {
                $value = sprintf('resource(%s)', get_resource_type($value));
            }
        };

        do {
            $trace = $traceProperty->getValue($exception);
            foreach($trace as &$call) {
                array_walk_recursive($call['args'], $flatten);
            }
            $traceProperty->setValue($exception, $trace);
        } while($exception = $exception->getPrevious());

        $traceProperty->setAccessible(false);
    }

Be aware to use this function.
As it changes real method arguments passed by reference.

function foo(&$bar)
{
    flattenExceptionBacktrace(new \Exception());
}

$bar = new \DateTime();
foo($bar);
var_dump($bar); // outputs: string(16) "object(DateTime)"

I did following to convert an exception into an array to be logged as json. Here I didn't care arguments

public function exceptiontoArray(null|Exception $exception)
{
    if($exception) {
      return [
        'message' => $exception->getMessage(),
        'file' => $exception->getFile(),
        'line' => $exception->getLine(),
        'trace' => $exception->getTrace(),
        'previous' => exceptiontoArray($exception->getPrevious())
      ];
    } else {
      return [];
    }
}

I use ReflectionObject to serialize exception, this dropped non-scalar properties, be careful.

function object2ScalarArray(object $object)
{
    $ref = new \ReflectionObject($object);

    $props = [];
    foreach ($ref->getProperties() as $prop) {
        $prop->setAccessible(true);
        $val = $prop->getValue($object);
        if (is_scalar($val)) {
            $props[$prop->getName()] = $val;
        }
    }

    return [
        'class' => $object::class,
        'props' => $props
    ];
}

function scalarArray2Object(array $scalarArray)
{
    $ref = new \ReflectionClass($scalarArray['class']);
    $object = $ref->newInstanceWithoutConstructor();

    $ref = new \ReflectionObject($object);

    foreach ($scalarArray['props'] as $name => $val) {
        $prop = $ref->getProperty($name);
        $prop->setAccessible(true);
        $prop->setValue($object, $val);
    }

    return $object;
}