src/web/ErrorHandler.php
public function renderPreviousExceptions($exception)
    {
        if (($previous = $exception->getPrevious()) !== null) {
            return $this->renderFile($this->previousExceptionView, ['exception' => $previous]);
        } else {
            return '';
        }
    }
public function renderPreviousExceptions($exception)
    {
        if (($previous = $exception->getPrevious()) !== null) {
            return $this->renderFile($this->previousExceptionView, ['exception' => $previous]);
        } else {
            return '';
        }
    }
Renders the previous exception stack for a given Exception.
@param \Exception $exception the exception whose precursors should be rendered.
@return string HTML content of the rendered previous exceptions.
Empty string if there are none.