Reset Class Instance Variables via Method

Question

Does anyone know how to reset the instance variables via a class method. Something like this:

class someClass 
{
    var $var1 = '';
    var $var2 = TRUE;

    function someMethod() 
    { 
        [...]
        // this method will alter the class variables
    }

    function reset()
    {
        // is it possible to reset all class variables from here?
    }
}

$test = new someClass();
$test->someMethod();
echo $test->var1;

$test->reset();
$test->someMethod();

I know I could simply do $test2 = new SomeClass() BUT I am particularly looking for a way to reset the instance (and its variables) via a method.

Is that possible at all???

Welcome to StackOverflow! Great first question.

Sampson
– Sampson

2009-12-21 22:08:05 +00:00
Commented Dec 21, 2009 at 22:08 — Sampson
– Sampson, Commented Dec 21, 2009 at 22:08

Victor Nicollet · Accepted Answer · 2009-12-21 22:18:24Z

8

You can use reflection to achieve this, for instance using get_class_vars:

foreach (get_class_vars(get_class($this)) as $name => $default) 
  $this -> $name = $default;

This is not entirely robust, it breaks on non-public variables (which get_class_vars does not read) and it will not touch base class variables.

answered Dec 21, 2009 at 22:18

Victor Nicollet

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5 Comments

Frank Over a year ago

that's exactly what I was looking for. thanks!! can you explain what you mean by "not touch base class vars"?

avpaderno Over a year ago

Victor Nicollet means the variables that are defined in the parent class. You could declare a class as class B extends A {}; A would be the base, or parent class.

Frank Over a year ago

okay. so that means that $test = new A(); $test->reset(); would work, whereas $test = new B(); $test->reset(); wouldnt. Right?

Victor Nicollet Over a year ago

Right. You could replace get_class($this) by a constant 'A' if you were afraid of this happening.

Frank Over a year ago

actually this won't apply to my code. but it's good to know! :)

Rob Lund · Accepted Answer · 2009-12-21 22:10:24Z

-1

Yes, you could write reset() like:

function reset()
{
    $this->var1 = array();
    $this->var2 = TRUE;
}

You want to be careful because calling new someClass() will get you an entirely new instance of the class completely unrelated to the original.

answered Dec 21, 2009 at 22:10

Rob Lund

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1 Comment

Frank Over a year ago

see above. that's what i am doing right now. but since there are 20+ properties it just seems redundant to do this. i thought maybe there's a php function or some kind of other trick for this...

streetparade · Accepted Answer · 2009-12-21 22:15:03Z

-1

this could be easy done;

public function reset()
{
    unset($this);
}

answered Dec 21, 2009 at 22:15

streetparade

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4 Comments

avpaderno Over a year ago

I tried it, but it doesn't reset any properties of the object.

streetparade Over a year ago

then you should try unset(get_class_methods($this));

streetparade Over a year ago

actualy php resets all object properties if the object is no more needed, try __destruct() put all your cleaning stuff there

Frank Over a year ago

since i want to reset them to the initial state unset wouldn't work (unless the initial state would be invoked by some method via the constructor)

Sampson · Accepted Answer · 2009-12-21 22:35:07Z

-1

Sure, the method itself could assign explicit values to the properties.

public function reset()
{
  $this->someString  = "original";
  $this->someInteger = 0;
}

$this->SetInitialState() from Constructor

Just as another idea, you could have a method that sets the default values itself, and is called from within the constructor. You could then call it at any point later as well.

<?php

  class MyClass {
    private $var;
    function __construct()     { $this->setInitialState(); }
    function setInitialState() { $this->var = "Hello World"; }
    function changeVar($val)   { $this->var = $val; }
    function showVar()         { print $this->var; }
  }

  $myObj = new MyClass();
  $myObj->showVar(); // Show default value
  $myObj->changeVar("New Value"); // Changes value
  $myObj->showVar(); // Shows new value
  $myObj->setInitialState(); // Restores default value
  $myObj->showVar(); // Shows restored value

?>

edited Dec 21, 2009 at 22:35

answered Dec 21, 2009 at 22:07

Sampson

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8 Comments

Frank Over a year ago

that's what I am doing right now. but since there's a LOT of properties in the class I thought there might be an easier solution to this...

Sampson Over a year ago

Frank, what about calling reset() from the Constructor to set the initial state?

Frank Over a year ago

wouldn't really make a difference, would it?

Sampson Over a year ago

Sure it would. The __construct() method would call $this->setInitialState() which sets the object properties to their default state. You can modify them with $this->someMethod(), and restore them with $this->setInitialState().

Sampson Over a year ago

Frank, you're going to have to have them all written someplace. What I'm suggesting is moving that task into the setInitialState() method, as opposed to immediately within your class.

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