Getting static property from a class with dynamic class name in PHP

dynamic, oop, php, properties, static

Solution

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.

Problem

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)

Original source

Related problems