public static function alnum($value, $message = null, $propertyPath = null)
{
try {
static::regex($value, '(^([a-zA-Z]{1}[a-zA-Z0-9]*)$)', $message, $propertyPath);
} catch (AssertionFailedException $e) {
$message = sprintf($message ?: 'Value "%s" is not alphanumeric, starting with letters and containing only letters and numbers.', static::stringify($value));
throw static::createException($value, $message, static::INVALID_ALNUM, $propertyPath);
}
return true;
}