php unserialize反系列化后为空处理

// utf8
function mb_unserialize($serial_str) {
$serial_str= preg_replace('!s:(\d+):"(.*?)";!se', "'s:'.strlen('$2').':\"$2\";'", $serial_str );
$serial_str= str_replace("\r", "", $serial_str);
return unserialize($serial_str);
}

// ascii
function asc_unserialize($serial_str) {
$serial_str = preg_replace('!s:(\d+):"(.*?)";!se', '"s:".strlen("$2").":\"$2\";"', $serial_str );
$serial_str= str_replace("\r", "", $serial_str);
return unserialize($serial_str);
}

<code>public function getSite()
{
$site = D('Setting')-&gt;field('v')-&gt;getByK('site');
$value = mb_unserialize($site['v']);
$this-&gt;response($value);
}</code>