How to create new property dynamically

How can I create a property from a given argument inside a object's method?

class Foo{

  public function createProperty($var_name, $val){
    // here how can I create a property named "$var_name"
    // that takes $val as value?

  }

}

And I want to be able to access the property like:

$object = new Foo();
$object->createProperty('hello', 'Hiiiiiiiiiiiiiiii');

echo $object->hello;

Also is it possible that I could make the property public/protected/private ? I know that in this case it should be public, but I may want to add some magik methods to get protected properties and stuff :)

---

I think I found a solution:

  protected $user_properties = array();

  public function createProperty($var_name, $val){
    $this->user_properties[$var_name] = $val;

  }

  public function __get($name){
    if(isset($this->user_properties[$name])
      return $this->user_properties[$name];

  }

do you think it's a good idea?

There are two methods to doing it.

One, you can directly create property dynamically from outside the class:

class Foo{
   
}

$foo = new Foo();
$foo->hello = 'Something';

Or if you wish to create property through your createProperty method:

class Foo{
    public function createProperty($name, $value){
        $this->{$name} = $value;
    }
}

$foo = new Foo();
$foo->createProperty('hello', 'something');

The following example is for those who do not want to declare an entire class.

$test = (object) [];

$prop = 'hello';

$test->{$prop} = 'Hiiiiiiiiiiiiiiii';

echo $test->hello; // prints Hiiiiiiiiiiiiiiii

Property overloading is very slow. If you can, try to avoid it. Also important is to implement the other two magic methods:

__isset(); __unset();

If you don't want to find some common mistakes later on when using these object "attributes"

Here are some examples:

http://www.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.members

EDITED after Alex comment:

You can check yourself the differences in time between both solutions (change $REPEAT_PLEASE)

<?php

 $REPEAT_PLEASE=500000;

class a {}

$time = time();

$a = new a();
for($i=0;$i<$REPEAT_PLEASE;$i++)
{
$a->data = 'hi';
$a->data = 'bye'.$a->data;
}

echo '"NORMAL" TIME: '.(time()-$time)."\n";

class b
{
        function __set($name,$value)
        {
                $this->d[$name] = $value;
        }

        function __get($name)
        {
                return $this->d[$name];
        }
}

$time=time();

$a = new b();
for($i=0;$i<$REPEAT_PLEASE;$i++)
{
$a->data = 'hi';
//echo $a->data;
$a->data = 'bye'.$a->data;
}

echo "TIME OVERLOADING: ".(time()-$time)."\n";

Use the syntax: $object->{$property} where $property is a string variable and $object can be this if it is inside the class or any instance object

Live example: http://sandbox.onlinephpfunctions.com/code/108f0ca2bef5cf4af8225d6a6ff11dfd0741757f

 class Test{
    public function createProperty($propertyName, $propertyValue){
        $this->{$propertyName} = $propertyValue;
    }
}

$test = new Test();
$test->createProperty('property1', '50');
echo $test->property1;

Result: 50