framework/base/ErrorHandler.php
public function handleHhvmError($code, $message, $file, $line, $context, $backtrace)
    {
        if ($this->handleError($code, $message, $file, $line)) {
            return true;
        }
        if (E_ERROR & $code) {
            $exception = new ErrorException($message, $code, $code, $file, $line);
            $ref = new \ReflectionProperty('\Exception', 'trace');
            $ref->setAccessible(true);
            $ref->setValue($exception, $backtrace);
            $this->_hhvmException = $exception;
        }

        return false;
    }
public function handleHhvmError($code, $message, $file, $line, $context, $backtrace)
    {
        if ($this->handleError($code, $message, $file, $line)) {
            return true;
        }
        if (E_ERROR & $code) {
            $exception = new ErrorException($message, $code, $code, $file, $line);
            $ref = new \ReflectionProperty('\Exception', 'trace');
            $ref->setAccessible(true);
            $ref->setValue($exception, $backtrace);
            $this->_hhvmException = $exception;
        }

        return false;
    }
Handles HHVM execution errors such as warnings and notices.

This method is used as a HHVM error handler. It will store exception that will
be used in fatal error handler

@param int $code the level of the error raised.
@param string $message the error message.
@param string $file the filename that the error was raised in.
@param int $line the line number the error was raised at.
@param mixed $context
@param mixed $backtrace trace of error
@return bool whether the normal error handler continues.

@throws ErrorException
@since 2.0.6