Moodle 2.1 or later requires at least PHP 5.3.2 (currently using version 5.2.6).
Some servers may have multiple PHP versions installed, are you using the correct executable?

The workaround ( http://www.webhostinghub.com/support/website/moodle/edit-lib-php-file-moodle )
does not work, the following lines of code are not in the lib.php file

public static function get_behaviour_required_behaviours($behaviour) {
$class = 'qbehaviour_' . $behaviour;
return $class::get_required_behaviours();
}