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.