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Subject: Accessing child constants from base class
From: dan@wep.net (Dan Cox)

PHP5 10/10/2003 CVS.

Currently, I don't see an easy way of accessing the constants of a child
class from a base class. Consider the following basic example:

abstract class myBaseClass {
  function getXML() {
    $doc = new domDocument();  
    $node = $doc->createElement(child::ElementName);
    $doc->appendChild($node);
    return $doc->saveXML($node);
  }
}

class myChildClass extends myBaseClass {
  const ElementName = 'foo';
  // ..lots of methods, etc here..
}

$foo = new myChildClass();
print($foo->getXML());


Of course, this does not work as there is no 'child::' accessor. The 
alternatives
to making this work are:

Use a protected variable in the child (and, of course, don't forget to 
also say
'protected $ElementName;' in the base class) and use $this->ElementName
for accessing the child's ElementName from the parent. This is probably good
enough, but much less than ideal.

Use this beautifully low maintenance, high performance piece of code in the
base class (not):

$className = get_class($this);
switch($className) {
  case 'mychildclass':
    $childElementName = myChildClass::ElementName;
  break;
  case 'myotherchildclass':
    $childElementName = myOtherChildClass::ElementName;
  break;
// etc.....
}
.... ick!

You may be able to shortcut the need for the switch statement with some
variable variable and/or eval() trickery, but let's not even go there..

So are there any plans on implementing child:: ? Is there a way of accessing
child constants without having to explicitly known the current and/or 
child class
name?

Any input appreciated-
Dan Cox