PHP, classes, "extends" and inheritance HELP

ppowell

class Parent {
  var $errorArray = array();

  function Parent() {
    return true;
  }

  function getErrorArray() {
    return $this->errorArray;
  }

  function setErrorArray($errorArray) {
   $this->errorArray = $this->errorArray + $errorArray;
  }

}

class Child1 extends Parent {

 function Child1() {
  return true;
 }

 function doStuff() {
   if ($this->isWrong) {
    $this->setErrorArray(array('action' => 'Oops!'));
   }
 }

}

class Child2 extends Parent {

 function Child2() {
  return true;
 }

 function doStuff() {
  if ($this->isWrong) {
   $this->setErrorArray(array('action' => 'Oops!'));
  }
 }

}

$child1 =& new Child();
$child1->doStuff();
print_r($child1->getErrorArray());
$child1 = null;

$child2 =& new Child();
$child2->doStuff();
print_r($child2->getErrorArray());
$child2 = null;

Ok, here is the simplest example of what I am trying to do. I have a near-pure-OO required setup of PHP where I am performing a Child1 object instance method doStuff(). If something goes wrong it sets its parents $this->errorArray. I will then perform a Child2 object instance method doStuff(). Same rules apply.

I want to see both errors filled out when I do my print_r() commands, but all I get is this:

Array ()

What am I doing wrong in my structure? I want all of my children classes of Parent all set up the same instance of $this->errorArray. Does it need to be static? What do I do?

Phil

ppowell

Actually, that's an inaccurate representation of the problem, my fault.. here is how it should be:

class Parent {
  var $errorArray = array();

  function Parent() {
    return true;
   }

   function getErrorArray() {
    return $this->errorArray;
   }

   function setErrorArray($errorArray) {
    $this->errorArray = $this->errorArray + $errorArray;
   }

}

class Child1 extends Parent {

  function Child1() {
    return true;
  }

  function doStuff() {
    if ($this->isWrong) { // IN THIS CASE ASSUME IT'S TRUE
     $this->setErrorArray(array('action1' => 'Oops from Child1'));
    }
   }

 }

class Child2 extends Parent {

  function Child2() {
    return true;
  }

  function doStuff2() {
    if ($this->isWrong) { // IN THIS CASE ASSUME IT'S TRUE
     $this->setErrorArray(array('action2' => 'Oops from Child2'));
    }
   }

}

class GrandChild1 extends Child1 {

  function GrandChild1() {
    return true;
  }

  function doMyStuff() {
   if ($this->isWrong) {
    $this->setErrorArray(array('action1.1' => 'Oops from GrandChild1'));
   }
   $child2 =& new Child2();
   if ($child2->isWrong) { // AGAIN, ASSUME IT'S TRUE
    print_r($this->getErrorArray());
   }
  }

}

$grandchild1 =& new GrandChild1();
$grandchild1->doStuff();
$grandchild1->doMyStuff();

Am I not right in assuming that the result should be:

Array ('action2' => 'Oops from Child2', 'action1.1' => 'Oops from GrandChild1')

Instead I get:

Array ()

what I ultimately have to do in my script is this:

In GrandChild1 Object I call an instance of Child2 Object to set an error array which I assume GrandChild1 should inherit since GrandChild1 extends Child1 extends Parent, while Child2 extends Parent, and Parent has the errorArray property and the Getter/Setter methods to change it.

Am I just off-balance here?

Thanx
Phil

ahundiak

I pasted your code into a file. Added
var $isError = true;
to the parent class and ran it.

It worked.

For PHP5 Parent is a reserved word.
Not sure about PHP4. I changed Parent to CParent.

ppowell

Actually that was an example of what I'm trying to do, the literal class name is not Parent (it's a very VERY long name!)

BTW I am using PHP 4.2.3 on one machine and 4.1.2(?) on the other.

Phil

ahundiak

It works under 4.3.4 as well.
I think you might have something else going on.

BTW, constructors cannot return values so
function Parent() {
return true; // Unnecessary and misleading
}

ppowell

Think I got it figured out, but now i'm not sure how to implement this, to coin a Java phrase:

What I need ultimately is the "Parent" class to have in its constructor a static array, $errorArray. That way every child class will have a static instance of $errorArray, something like:

$MyParentclass::errorArray

is that right?

Phil

ahundiak

Take a look at the user comments at the end of the chapter on objects for examples on dealing with static variables in PHP4.
http://www.php.net/manual/en/language.oop.php

PHP 5 supports static instance data directly.

ppowell

I used this example's structure in my code (using PHP 4.2.3):

class fooclass
{
   function &staticvar()
   {
       static $staticvar;
       return $staticvar;
   }

   function printme()
   {
       print($this->staticvar());
   }
}

$foo = new fooclass('foo');
$aid = & $foo->staticvar() ;
$aid = "Hello";
$foo->printme(); // Prints "Hello"
$aid = & $foo->staticvar() ;
$aid = "Foo";
$foo->printme(); // Prints "Foo"

This way to implement static class variables has as an advantage that you don't need to suse the same function to set and to get the value of a variable. The disadvantage is that you always need a helper variable.

Here is what I did:

class MethodGeneratorForActionPerformer {

  function &MethodGeneratorForActionPerformer() {
   static $errorArray = array();
  }

  function &getErrorArray() {
   return $this->errorArray;
  }

  function &setErrorArray($errorArray) {
   $this->errorArray =& $this->errorArray + $errorArray;
  }

}

class DBAction extends MethodGeneratorForActionPerformer {

  function DBAction() {} 

  function perform() {}

}

class FileGenerator extends MethodGeneratorForActionPerformer {

  var $db, $table;

  function FileGenerator($db, $table) {
   $this->db = $db;
   $this->table = table;
  }

  function doStuff() {
   if (somethingBreaks) {
    $this->setErrorArray(array('action' => 'You did something wrong here'));
   }
  }

}

class ActionPerformer extends DBAction {

  function ActionPerformer() {}

  function perform() {
    if (somethingBreaksHere) {
     $this->setErrorArray(array('subAction' => 'You did something wrong down here'));
    }
   }

}

Phil