话不多说直接上代码（如果有用的话-记得打赏哦）

/**
 * 从证书中获取私钥
 * @param $cert_path （微信平台证书---从《获取平台证书》接口中获得）
 * @return bool
 */
function certPubKey($cert_path){
    $cert_path = file_get_contents($cert_path);
    $pub_key  = openssl_pkey_get_public($cert_path);
    if($pub_key){
        $keyData = openssl_pkey_get_details($pub_key);
        return $keyData['key'];
    }
    return false;
}

/**
 * 验证回调主方法
 * @param $http_data header头的信息（微信回调发送的header头）
 * @param $body 应答主体信息 (微信发送的数据)(未解密的数据!!!)
 * @return int 验证成功返回 1  失败返回 0
 */

function verifySigns($http_data,$body){
        $wechatpay_timestamp    = $http_data['Wechatpay-Timestamp'];
        $wechatpay_nonce        = $http_data['Wechatpay-Nonce'];
        $wechatpay_signature    = $http_data['Wechatpay-Signature'];
        $signature = base64_decode($wechatpay_signature);
        $pub_key = certPubKey('wxpay_key/cert.pem');//平台证书路径
        $body = str_replace('\\','',$body);
        $message       =
            $wechatpay_timestamp . "\n" .
            $wechatpay_nonce . "\n" .
            $body . "\n";
        $res = openssl_verify($message,$signature, $pub_key,OPENSSL_ALGO_SHA256);

        if ($res == 1) {
            return 1;
        }
        return 0;
}