php - AFNetworking post到后端，数据怎么调用

Question

 let afn = AFHTTPRequestOperationManager()
     
        afn.POST("http://api.abc.com//index.php?s=/home/order/makeorder.html",parameters:
            ["data":"22222"], success: { (operation: AFHTTPRequestOperation!,
            responseObject: AnyObject!) in
            print("%@", operation.request.allHTTPHeaderFields);
            let data = responseObject as! NSDictionary!
            print("获取数据==%@",data)
            if data != nil {
                //   let dict: NSDictionary = (try! NSJSONSerialization.JSONObjectWithData(data!, options: .AllowFragments)) as! NSDictionary
              //  let modelTool = DictModelManager.sharedManager
              //  let data = modelTool.objectWithDictionary(data, cls: FreshHot.self) as? FreshHot
                
               // completion(data: data, error: nil)
            }
            },
                failure: { (operation: AFHTTPRequestOperation!,
                    error: NSError!) in
                    //Handle Error
                    print("获取数据出错=%@",error);
        })

后台用php 拿到的$_POST 数据为

a:1:{s:4:"data";s:5:"22222";}

试着对$_Post unserialize，可是得不到数据，，

file_get_contents('php://input') 得到的的数据是

s:10:"data=22222";

请问PHP 改怎么处理AFNetworking post过来的数据？