access property of object

To access public property of object in php, just use $obj->propertyname like:

class MyClass
{
  public $a;
};

$my=new MyClass;
$my->a=1;
echo $my->a;

Note that, unlike C++, you cannot use MyClass $my to create an instance of a class. You must use $my=new MyClass to initialize an object.

Unlike C++, you do not need to declare a variable in a class to use it:

class MyClass
{
};

$my=new MyClass;
$my->a=1;
echo $my->a;

When accessing an undeclared property, the __set function, if defined, will be called:

class MyClass
{
    public function __set($name,$value)//called
    {
        echo "set $name<br>";
        return $this->$name=$value;
    }
};

$my=new MyClass;
$my->a=1;
echo $my->a;

This does not apply to a declared (public) property:

class MyClass
{
    public $a;
    public function __set($name,$value) //not called
    {
        echo "set $name<br>";
        return $this->$name=$value;
    }
};

$my=new MyClass;
$my->a=1;
echo $my->a;

But the __set function is called when writing to a (declared) private/protected property:

class MyClass
{
    private $a;
    public function __set($name,$value) // called
    {
        echo "set $name<br>";
        return $this->$name=$value;
    }
};

$my=new MyClass;
$my->a=1;
echo $my->a;//fatal error

The reading of the private/protected property still fails with a fatal error. To read a private/protected property using the $obj->propertyname syntax, you need a getter function:

class MyClass
{
    private $a;
    
    public function __get($name)
    {
        echo "get $name<br>";
        return $this->a;
    }
    public function __set($name,$value) // called
    {
        echo "set $name<br>";
        return $this->$name=$value;
    }
};

$my=new MyClass;
$my->a=1;
echo $my->a;

Note that the setter function takes exactly two arguments, and the getter function must take exactly 1 argument, and we did not call the setter function __set and the getter function __get explicitly. They are called implicitly.

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