Getting static property from a class with dynamic

Question

I have this:

• one string variable which holds the class name ($classname)
• one string variable with holds the property name ($propertyname)

I want to get that property from that class, the problem is, the property is static and I don't know how to do that.

If the property weren't static, it would have been:

$classname->$propertyname;

if the property were a method, I could have used call_user_function

call_user_func(array($classname, $propertyname));

But in my case, am I just lost. I am however hoping that it is possible. With the thousands of functions that PHP has, he'd better have something for this as well. Maybe I'm missing something?

Thanks!

Edit:

• for those with eval() solutions: thanks, but it is out of the question
• for those with get _class _vars() solutions: thanks, but it seems it returns "the default properties of the given class" (php.net), and yes, I would like that value to be changable (even though it does help me in some of the cases)

Answer 1

I think this is the simplest:

$foo = new ReflectionProperty('myClassName', 'myPropertyName'); 
print $foo->getValue();

Answer 2

Getting and setting both static and non static properties without using Reflection

Using Reflection works but it is costly

Here is what I use for this purpose,

It works for PHP 5 >= 5.1.0 because I'm using property_exist

function getObjectProperty($object, $property)
{
    if (property_exists(get_class($object), $property)) {
        return array_key_exists($property, get_object_vars($object))
            ? $object->{$property}
            : $object::$$property;
    }
}

function setObjectProperty($object, $property, $value)
{
    if (property_exists(get_class($object), $property)) {
        array_key_exists($property, get_object_vars($object))
            ? $object->{$property} = $value
            : $object::$$property = $value;
    }
}

Answer 3

If you are using PHP 5.3.0 or greater, you can use the following:

$classname::$$propertyname;

Unfortunately, if you are using a version lower than 5.3.0, you are stuck using eval() (get_class_vars() will not work if the value is dynamic).

$value = eval($classname.'::$'.$propertyname.';');

---

EDIT: I've just said get_class_vars() wouldn't work if the value is dynamic, but apparently, variable static members are part of "the default properties of a class". You could use the following wrapper:

function get_user_prop($className, $property) {
  if(!class_exists($className)) return null;
  if(!property_exists($className, $property)) return null;

  $vars = get_class_vars($className);
  return $vars[$property];
}

class Foo { static $bar = 'Fizz'; }

echo get_user_prop('Foo', 'bar'); // echoes Fizz
Foo::$bar = 'Buzz';
echo get_user_prop('Foo', 'bar'); // echoes Buzz

Unfortunately, if you want to set the value of the variable, you will still need to use eval(), but with some validation in place, it's not so evil.

function set_user_prop($className, $property,$value) {
  if(!class_exists($className)) return false;
  if(!property_exists($className, $property)) return false;

  /* Since I cannot trust the value of $value
   * I am putting it in single quotes (I don't
   * want its value to be evaled. Now it will
   * just be parsed as a variable reference).
   */
  eval($className.'::$'.$property.'=$value;');
  return true;
}

class Foo { static $bar = 'Fizz'; }

echo get_user_prop('Foo', 'bar'); // echoes Fizz
set_user_prop('Foo', 'bar', 'Buzz');
echo get_user_prop('Foo', 'bar'); // echoes Buzz

set_user_prop() with this validation should be secure. If people start putting random things as $className and $property, it will exit out of the function as it won't be an existing class or property. As of $value, it is never actually parsed as code so whatever they put in there won't affect the script.

Answer 4

Potentially relevant: discussion on late static binding in PHP - When would you need to use late static binding?.

Answer 5

One thing I noticed is that you can't set variables which are protected in static classes as the eval() command runs in a scope outside the class. The only thing to get around this would be to implement a static method inside the/every class which runs the eval(). This method could be protected as the call_user_func() [to call the setter method] also runs from inside the class.