PHP递归函数内的静态变量

/**
 * 将数组转换为字符
 *
 * 用于缓存
 *
 * @param $data
 * @return string
 */
function philnaArray2String($data, $returns = '')
{
    static $t = 1;
    $tabType = " ";
    $tab = str_repeat($tabType, $t);
    $data = (array)$data;
    foreach ($data as $key => $value) {
        if (is_array($value)) {
            $t++;
            $returns .= "$tab'" . $key . "' => array(\n" . philnaArray2String($value) . "$tab),\n";
        } else {
            if (!is_bool($value)) {
                $value = "'" . addslashes($value) . "'";
            }
            $returns .= "$tab'" . $key . "' => $value,\n";
        }
    }
    $returns = substr_replace($returns, '', -2, -1);
    return $returns;
}