Iteration over $this and inheritance

tx34 · October 1, 2011

Hello, I have two classes:

abstract class Serializable
{
public function serialize()
{
	foreach($this as $member => $value)
	{
		$publicObject->$member = $value;
	}
	return $publicObject
}
}

class ToSerialize extends Serializable
{
public function otherSerialize()
{
	foreach($this as $member => $value)
	{
		$publicObject->$member = $value;
	}
	return $publicObject
}
}

$foo = new ToSerialize();
$foo->serialize(); //This will return one thing
$foo->otherSerialize(); //This will return something different

Why does this happen? :confused:

trq · October 1, 2011

That code will not execute due to several parse errors. Post your actual code.

tx34 · October 1, 2011

alright,

<?php

abstract class A_JsonSerializable 
{
  
    public function toJson()
    {
        foreach($this as $member => $value)
        {
            $publicObject->$member = $value;
        }
        return json_encode($publicObject);
    }

}

abstract class A_Polygon extends A_JsonSerializable
{
    
    private static $objectCount_ = 0;
    private $id_;
    private $shapeType_;    
    protected $coordinates_;
    
    public function __construct($shapeType = "Polygon") 
    {
        $this->id_ = self::$objectCount_;
        self::$objectCount_++;
        $this->shapeType_ = $shapeType;
    }

    public function otherToJson()
    {
        foreach($this as $member => $value)
        {
            $publicObject->$member = $value;
        }
        return json_encode($publicObject);
    }
    
}

class Hexagon extends A_Polygon
{   
    
    public function __construct($sideLength, Point $initialPoint) 
    {
        parent::__construct("Hexagon");

        $a = $sideLength * cos(M_PI / 6);
        $b = $sideLength * sin(M_PI / 6);
        
        $this->coordinates_[] = $initialPoint;
        $this->coordinates_[] = new Point($this->coordinates_[0]->x_ - $a, 
                                         $this->coordinates_[0]->y_ - $b);
        $this->coordinates_[] = new Point($this->coordinates_[1]->x_,
                                         $this->coordinates_[1]->y_ - $side);
        $this->coordinates_[] = new Point($this->coordinates_[0]->x_,
                                         $this->coordinates_[2]->y_ - b);
        $this->coordinates_[] = new Point($this->coordinates_[0]->x_ + a,
                                         $this->coordinates_[2]->y_);
        $this->coordinates_[] = new Point($this->coordinates_[4]->x_,
                                         $this->coordinates_[1]->y_);
    } 
    
}

function println($string)
{
    print($string . "<BR>");
}

$hex = new Hexagon(10, new Point(50, 50));
println($hex->otherToJson());
println($hex->toJson());

?>

This gives the output:

{"id_":0,"shapeType_":"Hexagon","coordinates_":[{"x_":50,"y_":50},{"x_":41.3397459622,"y_":45},{"x_":41.3397459622,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45}]}

{"coordinates_":[{"x_":50,"y_":50},{"x_":41.3397459622,"y_":45},{"x_":41.3397459622,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45}]}

When I used Zend_Json::encode($publicObject) I get "null" for the toJson() call.

trq · October 1, 2011

$publicObject is not defined anywhere in your code.

tx34 · October 1, 2011

I'm sorry but I do not understand, if it is not defined then how am I getting output from it?

trq · October 1, 2011

You shouldn't be. You should be getting errors about undefined variables. I'm still not convinced this is your actual code. Is the Point object being auto loaded? Otherwise, that is missing too.

tx34 · October 1, 2011

Damnit, I'm sorry! I double checked it this time to make sure:

<?php

class Point
{
    public $x_;
    public $y_;
    
    public function __construct($x, $y)
    {
        $this->x_ = $x;
        $this->y_ = $y;
    }    
}

abstract class A_JsonSerializable 
{
  
    public function toJson()
    {
        foreach($this as $member => $value)
        {
            $publicObject->$member = $value;
        }
        return json_encode($publicObject);
    }

}

abstract class A_Polygon extends A_JsonSerializable
{
    
    private static $objectCount_ = 0;
    private $id_;
    private $shapeType_;    
    protected $coordinates_;
    
    public function __construct($shapeType = "Polygon") 
    {
        $this->id_ = self::$objectCount_;
        self::$objectCount_++;
        $this->shapeType_ = $shapeType;
    }

    public function otherToJson()
    {
        foreach($this as $member => $value)
        {
            $publicObject->$member = $value;
        }
        return json_encode($publicObject);
    }
    
}

class Hexagon extends A_Polygon
{   
    
    public function __construct($sideLength, Point $initialPoint) 
    {
        parent::__construct("Hexagon");

        $a = $sideLength * cos(M_PI / 6);
        $b = $sideLength * sin(M_PI / 6);
        
        $this->coordinates_[] = $initialPoint;
        $this->coordinates_[] = new Point($this->coordinates_[0]->x_ - $a, 
                                         $this->coordinates_[0]->y_ - $b);
        $this->coordinates_[] = new Point($this->coordinates_[1]->x_,
                                         $this->coordinates_[1]->y_ - $side);
        $this->coordinates_[] = new Point($this->coordinates_[0]->x_,
                                         $this->coordinates_[2]->y_ - b);
        $this->coordinates_[] = new Point($this->coordinates_[0]->x_ + a,
                                         $this->coordinates_[2]->y_);
        $this->coordinates_[] = new Point($this->coordinates_[4]->x_,
                                         $this->coordinates_[1]->y_);
    } 
    
}

function println($string)
{
    print($string . "<BR>");
}

$hex = new Hexagon(10, new Point(50, 50));
println($hex->otherToJson());
println($hex->toJson());

?>

trq · October 1, 2011

Ok, so it's riddled with Notices but is still outputting results.

PHP Notice:  Undefined variable: side in /home/thorpe/foo.php on line 70

Notice: Undefined variable: side in /home/thorpe/foo.php on line 70
PHP Notice:  Use of undefined constant b - assumed 'b' in /home/thorpe/foo.php on line 72

Notice: Use of undefined constant b - assumed 'b' in /home/thorpe/foo.php on line 72
PHP Notice:  Use of undefined constant a - assumed 'a' in /home/thorpe/foo.php on line 73

Notice: Use of undefined constant a - assumed 'a' in /home/thorpe/foo.php on line 73
PHP Strict Standards:  Creating default object from empty value in /home/thorpe/foo.php on line 49

Strict Standards: Creating default object from empty value in /home/thorpe/foo.php on line 49
{"id_":0,"shapeType_":"Hexagon","coordinates_":[{"x_":50,"y_":50},{"x_":41.339745962156,"y_":45},{"x_":41.339745962156,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45}]}<BR>PHP Strict Standards:  Creating default object from empty value in /home/thorpe/foo.php on line 23

Strict Standards: Creating default object from empty value in /home/thorpe/foo.php on line 23
{"coordinates_":[{"x_":50,"y_":50},{"x_":41.339745962156,"y_":45},{"x_":41.339745962156,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45}]}<BR>

As for why your getting different output. It's a bit hard to explain. But if you declared all your properties within the Pont object it would be fine. Basically, when you are looping through $this it is picking up the properties of the class your function is defined in at the time it is defined.

tx34 · October 1, 2011

That is too bad, I was hoping I could just define it in one place, since I was planning to use it in a few different classes. I didn't even know I had warnings turned off. I am new to php, I am a C++ programmer. However after turning them on I do not not get quite as many warnings as you:

Notice: Undefined variable: side in /home/vol14/byethost22.com/b22_9075969/htdocs/forte/test.php on line 70

Notice: Use of undefined constant b - assumed 'b' in /home/vol14/byethost22.com/b22_9075969/htdocs/forte/test.php on line 72

Notice: Use of undefined constant a - assumed 'a' in /home/vol14/byethost22.com/b22_9075969/htdocs/forte/test.php on line 73

{"id_":0,"shapeType_":"Hexagon","coordinates_":[{"x_":50,"y_":50},{"x_":41.3397459622,"y_":45},{"x_":41.3397459622,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45}]}

{"coordinates_":[{"x_":50,"y_":50},{"x_":41.3397459622,"y_":45},{"x_":41.3397459622,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45},{"x_":50,"y_":45}]}

xyph · October 1, 2011

Because you aren't displaying strict errors.

How does a C++ programmer miss variable declarations?

tx34 · October 3, 2011

I was planning on replying earlier but I was having a fight to the death with my router. The C++ compiler is a lot less forgiving of my stupider moments, unlike php which seems to happily run no matter what garbage you give it. I came up with a solution for encoding private members, since I couldn't find something to do it for me. Although I probably wasn't looking hard enough or I was just being stupid again. It may not be the best solution, and the functions don't protect against user error, but it seems to be getting the job done so far.

<?php

abstract class A_JsonSerializable 
{
    abstract public function toJson();
    
    protected function element($name, $object)
    {
        $json = "\"" . $name . "\":";
        $json .= $this->processObject($object);
        return $json;
    }
    
    protected function native($name, $object)
    {
        $json = "\"" . $name . "\":";
        $json .= json_encode($object);
        return $json; 
    }
    
    private function processObject($object)
    {
        $json = "";
        if(is_array($object))
        {
            $json .= "[";
            for($i = 0; $i < count($object) - 1; $i++)
            {
                $json .= $object[$i]->toJson() . ","; 
            }
            $json .= $object[$i]->toJson() . "]";
        }
        else if(is_object($object))
        {
            $json .= $object->toJson();
        }
        return $json;
    }
    
    protected function bind()
    {
        $json = "{";
        for($i = 0; $i < func_num_args() - 1; $i++)
        {
            $json .= func_get_arg($i) . ",";
        }
        $json .= func_get_arg(func_num_args() - 1) . "}";
        return $json;
    }
    
    public function dump($fileName = "dump")
    {
        $handle = fopen($fileName . ".json", "w");
        fwrite($handle, $this->toJson());
        fclose($handle);
    }
}

?>

Example usage:

<?php

abstract class A_Polygon extends A_JsonSerializable
{   
    private static $objectCount_ = 0;
    private $id_;
    private $shapeType_;  
    
    protected $coordinates_;

    public function toJson()
    {
        return  $this->bind($this->native("id_", $this->id_), $this->element("coordinates_", $this->coordinates_));
    }   
}

?>

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Iteration over $this and inheritance

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