<?php
class StringCoordinateClass{
  private $arr=array('x'=>NULL,'y'=>NULL);

  function __get($property){
    if(array_key_exists($property,$this->arr)){
      return $this->arr[$property];
    }else{
      print "Error:Can't read a property other than x & y \n";
    }
  }

  function __set($property,$value){
    if(array_key_exists($property,$his->arr)){
      $this->arr[$property]=$value;
    }else{
      print "Error:Can't write a property other than x & y\n";
    }
  }
}

$obj=new StringCoordinateClass();
$obj->x=1;
print $obj->x;
print "\n";
$obj->n=2;
print $obj->n;
?>