src/Rules/Base64Trait.php
private function validateBase64($value)
    {
        $isNotValid = base64_decode($value, true) === false;
        if ($isNotValid) {
            $this->throwInvalidArgumentMustBe("valid base_64");
        }
    }
private function validateBase64($value)
    {
        $isNotValid = base64_decode($value, true) === false;
        if ($isNotValid) {
            $this->throwInvalidArgumentMustBe("valid base_64");
        }
    }
Allowed characters: A-Z, a-z, 0-9, +, /, =

@param $value