Dynamic class variables - php

Question

Does PHP have a method of having auto-generated class variables? I think I've seen something like this before but I'm not certain.
public class TestClass {
private $data = array();
public function TestClass() {
$this->data['firstValue'] = "cheese";
}
}
The $this->data array is always an associative array but they keys change from class to class. Is there any viable way to access $this->data['firstValue'] from $this->firstValue without having to define the link?
And if it is, are there any downsides to it?
Or is there a static method of defining the link in a way which won't explode if the $this->data array doesn't contain that key?

Answer 1

See here: http://www.php.net/manual/en/language.oop5.overloading.php
What you want is the "__get" method. There is an example for what you need on the link.

Answer 2

Use the PHP5 "magic" __get() method. It would work like so:
public class TestClass {
private $data = array();
// Since you're using PHP5, you should be using PHP5 style constructors.
public function __construct() {
$this->data['firstValue'] = "cheese";
}
/**
* This is the magic get function. Any class variable you try to access from
* outside the class that is not public will go through this method. The variable
* name will be passed in to the $param parameter. For this example, all
* will be retrieved from the private $data array. If the variable doesn't exist
* in the array, then the method will return null.
*
* #param string $param Class variable name
*
* #return mixed
*/
public function __get($param) {
if (isset($this->data[$param])) {
return $this->data[$param];
} else {
return null;
}
}
/**
* This is the "magic" isset method. It is very important to implement this
* method when using __get to change or retrieve data members from private or
* protected members. If it is not implemented, code that checks to see if a
* particular variable has been set will fail even though you'll be able to
* retrieve a value for that variable.
*
* #param string $param Variable name to check
*
* #return boolean
*/
public function __isset($param) {
return isset($this->data[$param]);
}
/**
* This method is required if you want to be able to set variables from outside
* your class without providing explicit setter options. Similar to accessing
* a variable using $foo = $object->firstValue, this method allows you to set
* the value of a variable (any variable in this case, but it can be limited
* by modifying this method) by doing something like:
* $this->secondValue = 'foo';
*
* #param string $param Class variable name to set
* #param mixed $value Value to set
*
* #return null
*/
public function __set($param, $value) {
$this->data[$param] = $value;
}
}
Using the magic __get, __set, and __isset constructors will allow you to control how you want variables to be set on a class while still storing all the values in a single array.
Hope this helps :)