static function define($definition_file)
{
if (!(file_exists($definition_file) and is_readable($definition_file))) {
throw new Exception('Unable to load polyfill definition file');
}
self::$polyfills = json_decode(file_get_contents($definition_file), true);
foreach (self::$polyfills as $name => $polyfill) {
$version = $polyfill['since'];
if (!isset(self::$versions[$version])) {
self::$versions[$version] = array();
}
self::$versions[$version][] = $name;
}
}
