private function initializeVariables($value)
    {
        preg_match_all('/\$([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)/', $value, $matches);

        foreach (array_unique($matches[0]) as $variable) {
            $value = "<?php $variable = isset($variable) ? $variable : null; ?>\n".$value;
        }

        return $value;
    }