ReflectionClass::setStaticPropertyValue

Calling this method on a static property that is not public will return a ReflectionException stating the property does not exist. This is quite misleading as the property is valid.
class test {
 public static $publicProperty = 'public';
 private static $privateProperty = 'private';
 public static function printProperties() {
 echo self::$publicProperty . "\n";
 echo self::$privateProperty . "\n";
 }
} 
$reflectedClass = new \ReflectionClass('test');
$reflectedClass->setStaticPropertyValue('publicProperty', 'foo');
$reflectedClass->setStaticPropertyValue( 'privateProperty', 'bar' );
PHP Fatal error: Uncaught exception 'ReflectionException' with message 'Class test does not have a property named privateProperty'
If you retrieve the method using the reflection class getProperty method you can circumnavigate this issue
$reflectedProperty = $reflectedClass->getProperty('privateProperty');
$reflectedProperty->setAccessible(true);
$reflectedProperty = $reflectedProperty->setValue('bar');
test::printProperties(); 
will echo
foo
bar

It is important to note that calling ReflectionClass::setStaticPropertyValue will not allow you to add new static properties to a class.