PHP OOP, perform a function once a certain variable has been set

Question

How can i perform a function once a variable's value has been set?

say like

$obj = new object(); // dont perform $obj->my_function() just yet
$obj->my_var = 67    // $obj->my_function() now gets run

I want the object to do this function and now having to be called by the script.

Thanks

EDIT my_var is predefined in the class, __set is not working for me.

Answer 1

I'd recommend to create a setter function for $obj and include the relevant function call there. So basically your code would look somehow like this:

$obj = new ClassOfYours();
$obj->setThatValue("apple");

Of course you would have to take care that all assignments to ThatValue need to be done through that setter in order make it work properly. Assuming that you're on php5 I'd set that property to private, so all direct assignments will cause an runtime error.

A good overview about OOP in php can be found in this article on devarticles.com.

HTH

Answer 2

To acheive exactly what you describe, you'd have to use a magic setter.

class ObjectWithSetter {

    var $data = array();

    public function my_function() {
        echo "FOO";
    }


    public function __set($name, $value) {
        $this->data[$name] = $value;
        if($name == 'my_var') {
            $this->my_function();
        }
    }

    public function __get($name) {
        if (array_key_exists($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;
    }

    /**  As of PHP 5.1.0  */
    public function __isset($name) {
        return isset($this->data[$name]);
    }

    public function __unset($name) {
        unset($this->data[$name]);
    }

}

Answer 3

Assuming you want to call my_function() once you set a value, that case you can encapsulate both the operations into one. Something like you create a new function set_my_var(value)

function set_my_var(varvalue)
{
$this->my_var = varvalue;
$this->my_function();
}

Answer 4

Use a private property so __set() is invoked:

class Myclass {
  private $my_var;
  private $my_var_set = false;

  public function __set($var, $value) {
    if ($var == 'my_var' && !$this->my_var_set) {
      // call some function
      $this->my_var_set = true;
    }
    $this->$var = $value;
  }

  public function __get($var, $value) {
    return $this->$name;
  }
}

See Overloading. __set() is called because $my_var is inaccessible and there is your hook.