PHP set and get overloading in inheritance

Question

I am implementing an OOP design using PHP. I wonder how PHP handles inheritance for its magic methods like __get and __set.

class Foo
{
    protected $property1;

    public function __get($name)
    {
        if ($name == "property1")
        {
            // do some logic
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if ($name == "property1")
        {
            // do some logic
            return $result; // may be null
        }
        result;
    }
}

Now for extending Foo:

class Bar extends Foo
{
    protected $property2;

    public function __get($name)
    {
        if (($result = parent::__get($name)) !== null)
            return $result; // may be null
        if ($name == "property2")
        {
            // do some logic
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if (($result = parent::__set($name, $value)) !== null)
            return $result; // may be null
        if ($name == "property2")
        {
            // do some logic
            return $result; // may be null
        }
        return;
    }
}

As PHP returns null as the result of a function with nothing to return... this may lead in ambiguity of whether the parent::__get() or parent::__set() returned null truely or returned with no value; and leads to overhead.

Now if PHP considers the static::_get() and static::__set() first and fall backs to the parent versions on failure, this could be simplified as:

class Bar extends Foo
{
    protected $property2;

    public function __get($name)
    {
        if ($name = "property2")
        {
            // do some logic
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if ($name = "property2")
        {
            // do some logic
            return $result; // may be null
        }
        return;
    }
}

I can't test it on current implementation because the classes in context manipulates production, live database. Which is the correct implementation?

Thanks!

"the classes in context manipulates production, live database" -- consider setting up a development environment with a dummy database. Having only a production environment limits your development capabilities severely. — Elias
– Elias, Commented Oct 21, 2014 at 14:52
you seem to have bugs in code if ($name = "property2") - I assume you wanted to use if ($name === "property2") — Valter
– Valter, Commented Oct 21, 2014 at 14:55
Thank you @Elias! I managed to create a dummy for my purpose. — Tala
– Tala, Commented Oct 21, 2014 at 15:15
Thank you @Valter ! I have some typos in above code that is fixed now. — Tala
– Tala, Commented Oct 21, 2014 at 15:15
Or simply don't use magic getters/setters at all (other than to throw Exception possibly) and enforce proper use of the defined getter/setter functions. After all the properties were made inaccessible for a reason right? — Mike Brant
– Mike Brant, Commented Oct 21, 2014 at 15:34

BreyndotEchse · Accepted Answer · 2014-10-21 15:27:04Z

3

Use magic methods only as proxy methods. Your code will be much cleaner and you don't have to deal with problems caused by inheritance.

Simple example:

class Foo
{
    protected $property1;

    public function setProperty1($property1)
    {
        // do some logic
        $this->property1 = $property1;
        return $this;
    }

    public function getProperty1()
    {
        // do some logic
        return $this->property1;
    }

    public function __get($name)
    {
        $method = 'get' . ucfirst($name);
        if (method_exists($this, $method)) {
            return $this->$method();
        }
    }

    public function __set($name, $value)
    {
        $method = 'set' . ucfirst($name);
        if (method_exists($this, $method)) {
            $this->$method($value);
        }
    }
}

class Bar extends Foo
{
    protected $property2;

    public function setProperty2($property2)
    {
        // do some logic
        $this->property2 = $property2;
        return $this;
    }

    public function getProperty2()
    {
        // do some logic
        return $this->property2;
    }
}

Example call:

$bar = new Bar;
$bar->property1 = 'foo';
$bar->property2 = 'bar';
var_dump($bar);

answered Oct 21, 2014 at 15:27

BreyndotEchse

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3 Comments

Tala Over a year ago

Thanks! This is brilliant! but I guess instead of $this I should provide method_exists with static to work for inheritance!

Mike Brant Over a year ago

Of course if you go through the exercise of defining proper getter/setter functions then you have no need for the magic functions at all other than to allow a more lax access paradigm (i.e. $object->property instead of $object->getProperty()) by the caller.

Tala Over a year ago

@MikeBrant it can be more complex. There are times when the getter/setter methods are set as private or protected for packaging. That way, the proxy looks neat. Though the end user doesn't have direct access to call $object->getProperty abundantly, it can access it through trying to reach an inaccessible property by $object->userFriendlyNameForProperty.

Tala · Accepted Answer · 2014-10-21 15:25:36Z

I have managed to create an Isolated environment and test both methods.

Method 1

class Foo
{
    protected $property1;

    public function __get($name)
    {
        if ($name == "name")
        {
            echo "been here @line(" . __LINE__ . ") Foo::__get('$name') <br/>";
            $result = $this->property1;
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if ($name == "name")
        {
            echo "been here @line(" . __LINE__ . ") Foo::__set('$name', '$value') <br/>";
            $result = $this->property1 = $value;
            return $result; // may be null
        }
        return;
    }
}

class Bar extends Foo
{
    protected $property2;

    public function __get($name)
    {
        if ($name == "place")
        {
            echo "been here @line(" . __LINE__ . ") Bar::__get('$name') <br/>";
            $result = $this->property2;
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if ($name == "place")
        {
            echo "been here @line(" . __LINE__ . ") Bar::__set('$name', '$value') <br/>";
            $result = $this->property2 = $value;
            return $result; // may be null
        }
        return;
    }
}

$bar = new Bar;

$bar->name = 'Alice';
$bar->place = 'Wonderland';

echo "done that: '{$bar->name} in {$bar->place}'";

The above code results are:

been here @line(59) Bar::__set('place', 'Wonderland') 
been here @line(43) Bar::__get('place') 
done that: ' in Wonderland'

That is clearly not the answer.

Method 2

class Foo
{
    protected $property1;

    public function __get($name)
    {
        if ($name == "name")
        {
            echo "been here @line(" . __LINE__ . ") Foo::__get('$name') <br/>";
            $result = $this->property1;
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if ($name == "name")
        {
            echo "been here @line(" . __LINE__ . ") Foo::__set('$name', '$value') <br/>";
            $result = $this->property1 = $value;
            return $result; // may be null
        }
        return;
    }
}

class Bar extends Foo
{
    protected $property2;

    public function __get($name)
    {
        if (($result = parent::__get($name)) !== null)
        {
            echo "been here @line(" . __LINE__ . ") parent::__get('$name') <br/>";
            return $result; // may be null
        }
        if ($name == "place")
        {
            echo "been here @line(" . __LINE__ . ") Bar::__get('$name') <br/>";
            $result = $this->property2;
            return $result; // may be null
        }
        return;
    }

    public function __set($name, $value)
    {
        if (($result = parent::__set($name, $value)) !== null)
        {
            echo "been here @line(" . __LINE__ . ") parent::__set('$name', '$value') <br/>";
            return $result; // may be null
        }
        if ($name == "place")
        {
            echo "been here @line(" . __LINE__ . ") Bar::__set('$name', '$value') <br/>";
            $result = $this->property2 = $value;
            return $result; // may be null
        }
        return;
    }
}

$bar = new Bar;

$bar->name = 'Alice';
$bar->place = 'Wonderland';

echo "done that: '{$bar->name} in {$bar->place}'";

Which results in:

been here @line(22) Foo::__set('name', 'Alice') 
been here @line(54) parent::__set('name', 'Alice') 
been here @line(59) Bar::__set('place', 'Wonderland') 
been here @line(11) Foo::__get('name') 
been here @line(38) parent::__get('name') 
been here @line(43) Bar::__get('place') 
done that: 'Alice in Wonderland'

This is the correct answer for overloading __get and __set magic functions while dealing with inheritance, but this has overheads. It is a solution but is there any better solution?

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