How/Can I implement a class has-a class relationship?

I have been programing with PHP for a little bit.  I know enough to do some basic things but I want to organize my code and get more OO based.

I am trying to make a class that has classes. Is that possible and if so, what am I doing wrong here:

Attached is my code.

This is my error message:

Fatal error: Cannot access empty property in /home/frank/dev/www/cogiw2008/newclass.php on line 32

<?php
  // class declaration
class AMember
{
  protected $var1;
  protected $var2;
 
  function loadclass($var1, $var2)
  {
    $this->var1=$var1;
    $this->var2=$var2;
  }
 
  function display()
  {
    echo $this->var1."<br>";
    echo $this->var2."<br>";
  }
}
class aClass
{
  protected $_aMemberClass;
  protected $_aMemberVar;
 
function  _construct()
    {
      echo "constructing<br>\n";
    }
 
  function loadAMemberClass($var1, $var2)
  {
    $this->$_aMemberClass =& new AMember();
    $this->$_aMemberClass->loadclass($var1, $var2);
    $this->$_aMemberVar = "Hi I\'m a membervar";
  }
 
  function display()
  {
    $this->$_aMemberClass->display();
    echo $this->$_aMemberVar."<br>\n";
  }
 
}
 
/// end of class declaration
 
$class =& new aClass();
$class->loadAMemberClass("This is var1 one of member class","This is var2 one of member class" );
$class->display();
?>

Select allOpen in new window