PHP通过引用设置类成员

Question

I'm trying to build a JSON server response in php. As the server run through the script I use an array in my output to keep track of errors and successes in the script. Like in the code below.

<?php
$output = array();
$output["success"] = array();
$output["error"] = array();

public function foo(){
    global $output;
    $db = database::getInstance(); //initialize singleton instance
    $db->setOutput($output);       //set Output log
    $db->login();                  //log user in

    $output["success"][] = "method end"; //debug breakpoint
}

echo json_encode($output, JSON_HEX_QUOT | JSON_HEX_TAG);

And the database class looks something like this...

<?php
namespace db;
class database{
    private var $output_log;

    public function setOutputLog(&$output){
        $this->output_log = $output; 
    }

    public function login(){
        ...

        $this->output_log["error"][] = "login error";

        ...
    }
}

And the when I run the script the output is always something like this...

{
   "success" : ["method end"],
   "error" : []
}

The problem seems to be when I try to pass $output by reference to the singleton instance of the database class or in the call to json_encode(). I have looked all over and this is the only way to pass by reference, but the funny thing is if there is an error in the database JSON.parse() in the javascript throws the error, and the output isn't a php error log. Anyway, know a way around this by passing the reference of $output because there are gonna be times when I expect $output to get pretty big and I want to keep the copies of the array to a minimum and I really am no good with php array functions plus if I did something like this. $output["error"][] = $db->login(); and changed login method to return the $output_log I would end up with this.

{
   "success" : ["method end"],
   "error" : ["error":["login error"]]
}

EDIT: The changes I made base upon your answers in case anyone needs it. I went on to make a response namespace with two classes that are gonna my life sooo much easier.

Response.php

namespace response;
class json_builder
{
    private static $instance;
    private $output;

    private function __construct(){
        $this->output = array();
    }

    public static function getInstance(){
        if(is_null(self::$instance)){
            self::$instance = new self();
        }
        return self::$instance;
    }

    public function addLine($tag, $msg){
        $this->output[$tag] = $msg;
    }

    public function remove($tag){
        unset($this->output[$tag]);
    }

    public function addArray($tag){
        $this->output[$tag] = array();
    }

    public function addArrayLine($tag, $msg){
        array_push($this->output[$tag], $msg); 
    }

    public function export($filter){
       echo json_encode($this->output, $filter);
       unset($this->output);
    }
}

class xml_builder
{
    private static $instance;
    private $output;

    private function __construct(){
        $this->output = "<?xml version=\"1.0\"?>";
    }

    public static function getInstance(){
        if(is_null(self::$instance)){
            self::$instance = new self();
        }
        return self::$instance;
    }

    public function addNode($tag, $msg, $attributes){
        $this->output += ($attributes) ? "<"+$tag+" "+$attributes+">" : "<"+$tag+">";
        $this->output += $msg + "</"+$tag+">";
    }

    public function startNode($tag, $msg, $attributes){
        $this->output += ($attributes) ? "<"+$tag+" "+$attributes+">" : "<"+$tag+">";
    }

    public function endNode($tag){
        $this->output += "</"+$tag+">";
    }

    public function addInput($msg){
        $this->output += $msg;
    }

    public function export(){
       echo $this->output;
       unset($this->output);
    }
}

and the new code from before would look like this

valid.php -> starting point

<?php
require_once "response.php";
require_once "db.php";

$output = /response/json_builder::getInstance();
$output->addArray("success");
$output->addArray"error");

public function foo(){
    $output = /response/json_builder::getInstance();
    $db = database::getInstance(); //initialize singleton instance
    $db->login();                  //log user in

    $output->addArrayLine("success", "method end"); //debug breakpoint
}

$output->export(JSON_HEX_QUOT | JSON_HEX_TAG);

db.php -> database class

<?php
namespace db;
class database{
    private $xml_output;
    private $json_output;

    private function __construct()
    {
        $this->json_output = \response\json_builder::getInstance();
        $this->xml_output = \response\xml_builder::getInstance();
    }

    public static function getInstance()
    {
         if(is_null(self::$instance))
         {
              self::$instance = new self();
         }
         return self::$instance;
    }

    public function login(){
        ...

        $this->output->addArrayLine("error", "login error");

        ...
    }
}

Thanks for the help Wizard and Chris. =)

Answer 1

try to set it as:

public function setOutputLog(&$output){
    $this->output_log = &$output; 
}

but global variables are evil :)

Answer 2

Avoid nasty global variables and do it OOP way. Use OutputLog class as a dependency of Database class.

class OutputLog
{
   protected $log = [];

   public add($line) {
       $this->log[] = $line;
   }

   public all() {
       return $this->log;
   }
}

class Database
{
   protected $success;
   protected $error;

   public function __construct(OutputLog $success, OutputLog $error)
   {
      $this->success = $success;
      $this->error   = $error;
   }

   public function login()
   {
      // Code
      $this->error->add('Login Error');
      $this->success->add('Login Successful');
   }
}

$error   = new OutputLog();
$success = new OutputLog();

$db = new Database($success, $error);
$db->login();

$success->add('Main End');

echo( json_encode( [ $success->all(), $error->all() ] ) );