PHP如何实现Token验证

<?php
function check_token($token) {
    /**** api传来的token ****/
    if(!isset($token) || empty($token)) {
        $msg[&#39;code&#39;]=&#39;400&#39;;
        $msg[&#39;msg&#39;]=&#39;非法请求&#39;;
        return json_encode($msg,JSON_UNESCAPED_UNICODE);
    }
    //对比token
    $explode = explode(&#39;.&#39;,$token);
    //以.分割token为数组
    if(!empty($explode[0]) && !empty($explode[1]) && !empty($explode[2]) && !empty($explode[3]) ) {
        $info = $explode[0].&#39;.&#39;.$explode[1].&#39;.&#39;.$explode[2];
        //信息部分
        $true_signature = hash_hmac(&#39;md5&#39;,$info,&#39;siasqr&#39;);
        //正确的签名
        if(time() > $explode[2]) {
            $msg[&#39;code&#39;]=&#39;401&#39;;
            $msg[&#39;msg&#39;]=&#39;Token已过期,请重新登录&#39;;
            return json_encode($msg,JSON_UNESCAPED_UNICODE);
        }
        if ($true_signature == $explode[3]) {
            $msg[&#39;code&#39;]=&#39;200&#39;;
            $msg[&#39;msg&#39;]=&#39;Token合法&#39;;
            return json_encode($msg,JSON_UNESCAPED_UNICODE);
        } else {
            $msg[&#39;code&#39;]=&#39;400&#39;;
            $msg[&#39;msg&#39;]=&#39;Token不合法&#39;;
            return json_encode($msg,JSON_UNESCAPED_UNICODE);
        }
    } else {
        $msg[&#39;code&#39;]=&#39;400&#39;;
        $msg[&#39;msg&#39;]=&#39;Token不合法&#39;;
        return json_encode($msg,JSON_UNESCAPED_UNICODE);
    }
}