Constructors and Destructors

__construct constructor

Class calls this method every time a new object is created, so it's a good place to do some initialization before using the object.

__deconstruct

Destructors execute when all references to an object are deleted or when the object is explicitly destroyed.

<?php
class MyDestructableClass {
    public $name;
   function __construct() {
       print "In constructor\n";
       $this->name = "MyDestructableClass";
   }

   function __destruct() {
       print "Destroying " . $this->name . "\n";
   }
}

$obj = new MyDestructableClass();
?>

Method overloading

public __call ( string $name , array $arguments ) : mixed
public static __callStatic ( string $name , array $arguments ) : mixed

When an invocation method is invoked in an object, __call() is called.

When an invocation method is invoked in a static context, __callStatic() is called.

Property Override

public __set ( string $name , mixed $value ) : void
public __get ( string $name ) : mixed
public __isset ( string $name ) : bool
public __unset ( string $name ) : void

• When assigning a value to an inaccessible property, \.
• When reading the value of an inaccessible property, \.
• When isset() or empty() is called on an inaccessible property, u isset() is called.
• When unset() is called on an inaccessible property, \.

Parameter name is the name of the variable to operate on.

• __The name of the set() method is the name of the variable to operate on.
• __The value parameter of the set() method specifies the value of the $name variable.

Property overloading can only occur in objects. In static methods, these magic methods will not be called. So none of these methods can be declared static.

<?php
class PropertyTest {
     /**  The overloaded data is saved here  */
    private $data = array();

 
     /**  Overloads cannot be used on defined properties  */
    public $declared = 1;

     /**  Overload occurs only when this property is accessed from outside the class */
    private $hidden = 2;

    public function __set($name, $value) 
    {
        echo "Setting '$name' to '$value'\n";
        $this->data[$name] = $value;
    }

    public function __get($name) 
    {
        echo "Getting '$name'\n";
        if (array_key_exists($name, $this->data)) {
            return $this->data[$name];
        }

        $trace = debug_backtrace();
        trigger_error(
            'Undefined property via __get(): ' . $name .
            ' in ' . $trace[0]['file'] .
            ' on line ' . $trace[0]['line'],
            E_USER_NOTICE);
        return null;
    }

    /**  PHP 5.1.0 Later version */
    public function __isset($name) 
    {
        echo "Is '$name' set?\n";
        return isset($this->data[$name]);
    }

    /**  PHP 5.1.0 Later version */
    public function __unset($name) 
    {
        echo "Unsetting '$name'\n";
        unset($this->data[$name]);
    }

    /**  Non magic method  */
    public function getHidden() 
    {
        return $this->hidden;
    }
}


echo "<pre>\n";

$obj = new PropertyTest;

$obj->a = 1;
echo $obj->a . "\n\n";

var_dump(isset($obj->a));
unset($obj->a);
var_dump(isset($obj->a));
echo "\n";

echo $obj->declared . "\n\n";

echo "Let's experiment with the private property named 'hidden':\n";
echo "Privates are visible inside the class, so __get() not used...\n";
echo $obj->getHidden() . "\n";
echo "Privates not visible outside of class, so __get() is used...\n";
echo $obj->hidden . "\n";
?>

__toString()public
__toString ( void ) : string
__The toString() method is used for how a class should respond when it is treated as a string.

For example, echo $obj; what should be displayed.
This method must return a string, otherwise it will issue a fatal error with the level of "e" recoverable "error.

<?php
// Declare a simple class
class TestClass
{
    public $foo;

    public function __construct($foo) 
    {
        $this->foo = $foo;
    }

    public function __toString() {
        return $this->foo;
    }
}

$class = new TestClass('Hello');
echo $class;
?>

__invoke()
__invoke ([ $... ] ) : mixed

When you try to call an object as a function, the \.

<?php
  class CallableClass 
  {
      function __invoke($x) {
          var_dump($x);
      }
  }
  $obj = new CallableClass;
  $obj(5);
  var_dump(is_callable($obj));
  ?>