wol-soft/php-json-schema-model-generator

$additionalProperties =  (static function () use ($modelData): array {
    $additionalProperties = array_diff(array_keys($modelData), {{ properties }});

    {% if pattern %}
        // filter out all pattern properties
        $additionalProperties = array_filter(
            $additionalProperties,
            static function (string $property): bool {
                return preg_match('/{{ pattern }}/', $property) !== 1;
            }
        );
    {% endif %}

    return $additionalProperties;
})()