Forward declarations in PHP

[Gilesey]

I'm just learning php, but am an expert in C++ and others.

Can you tell me if forward declarations are allowed for classes?

E.g. if I'm representing a relationship between two classes, and they are allowed to know about each other. This is more appropriate when abstracting database tables as classes, where such relationships will exist.

Note, this example is contrived, I don't have any such class called source and target, and it probably doesn't compile. But it would be nice to have this association.

class Source
{
// constructors etc..removed

function FindTarget()
{
return new Target();
}
}

and a similar class target
class Target
{
// constructors etc.. removed
function FindSource()
{
return new Source();
}
}

I tried placing

class Target;

before the declaration of class Source, but the compiler spurted errors at me.

Is there a way of forward declaring a class or not?

Thanks in advance

Giles

[mrhappiness]

class source
{
  var $target = NULL;
  var $name = '';
  function source($name = 'source', $target = NULL)
  {
    $this->name = $name;
    if (is_null($target))
      $this->target = &new target('target of source', $this);
  }

  function info()
  {
    echo "Hi: I'm ".$this->name."<br />";
    echo 'My target is called: '.$this->target->name.'<br />';
    if ($call_target)
      echo $this->target->info();
  }
}


class target
{
  var $source = NULL;
  var $name = '';
  function target($name = 'target', $source = NULL)
  {
    $this->name = $name;
    if (is_null($source))
      $this->source = &new source('source of target', $this);
  }

  function info()
  {
    echo "Hi: I'm ".$this->name."<br />";
    echo 'My source is called: '.$this->source->name.'<br />';
  }
}

will work just fine

[Gilesey]

wow, nice reply thanks.

So can I assume to get my FindTarget function, as I wanted it above...

class source
{
...
function FindTarget()
{
  if (is_null($this->target)) 
      $this->target = &new target('target of source', $this); 
    return $this->target;
}
}

$psource = new source('blah');
$ptarget = $psource->FindTarget();

The tools I was lacking, were the dummy declaration of

$this->target;

and the weird looking (address of?) operator

 $this->target  = &new target('target of source', $this); 

which I haven't seen yet. I'm not sure why it suddenly would find the class 'target' in your example, but I'm sure it will become clear soon.

I'm such a noob!

I will try these things out tonight, thanks a lot.