Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires php ^8.0 but your php version (7.4.33) does not satisfy that requirement.

Process completed with exit code 2.

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainType: Cannot resolve types for $this->lastRefreshOn with type DateTimeInterface and !isset assertion (see https://psalm.dev/056)

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainNull: Cannot resolve types for $this->lastRefreshOn - DateTimeInterface does not contain null (see https://psalm.dev/090)

src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php:24:5: MethodSignatureMismatch: Method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection::__construct has fewer parameters than parent method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\AbstractFeaturesCollection::__construct (see https://psalm.dev/042)

src/Model/Subscription.php:41:13: ParseError: Union types are not supported in PHP < 8 (see https://psalm.dev/173)

src/Model/Subscription.php:129:36: InvalidReturnType: The declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures is incorrect, got 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' (see https://psalm.dev/011)

src/Model/Subscription.php:131:16: InvalidReturnStatement: The inferred type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' does not match the declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures (see https://psalm.dev/128)

Process completed with exit code 2.

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainType: Cannot resolve types for $this->lastRefreshOn with type DateTimeInterface and !isset assertion (see https://psalm.dev/056)

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainNull: Cannot resolve types for $this->lastRefreshOn - DateTimeInterface does not contain null (see https://psalm.dev/090)

src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php:24:5: MethodSignatureMismatch: Method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection::__construct has fewer parameters than parent method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\AbstractFeaturesCollection::__construct (see https://psalm.dev/042)

src/Model/Subscription.php:41:13: ParseError: Union types are not supported in PHP < 8 (see https://psalm.dev/173)

src/Model/Subscription.php:129:36: InvalidReturnType: The declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures is incorrect, got 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' (see https://psalm.dev/011)

src/Model/Subscription.php:131:16: InvalidReturnStatement: The inferred type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' does not match the declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures (see https://psalm.dev/128)

Process completed with exit code 2.

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainType: Cannot resolve types for $this->lastRefreshOn with type DateTimeInterface and !isset assertion (see https://psalm.dev/056)

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainNull: Cannot resolve types for $this->lastRefreshOn - DateTimeInterface does not contain null (see https://psalm.dev/090)

src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php:24:5: MethodSignatureMismatch: Method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection::__construct has fewer parameters than parent method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\AbstractFeaturesCollection::__construct (see https://psalm.dev/042)

src/Model/Subscription.php:41:13: ParseError: Union types are not supported in PHP < 8 (see https://psalm.dev/173)

src/Model/Subscription.php:129:36: InvalidReturnType: The declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures is incorrect, got 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' (see https://psalm.dev/011)

src/Model/Subscription.php:131:16: InvalidReturnStatement: The inferred type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' does not match the declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures (see https://psalm.dev/128)

Process completed with exit code 2.

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainType: Cannot resolve types for $this->lastRefreshOn with type DateTimeInterface and !isset assertion (see https://psalm.dev/056)

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainNull: Cannot resolve types for $this->lastRefreshOn - DateTimeInterface does not contain null (see https://psalm.dev/090)

src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php:24:5: MethodSignatureMismatch: Method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection::__construct has fewer parameters than parent method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\AbstractFeaturesCollection::__construct (see https://psalm.dev/042)

src/Model/Subscription.php:41:13: ParseError: Union types are not supported in PHP < 8 (see https://psalm.dev/173)

src/Model/Subscription.php:129:36: InvalidReturnType: The declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures is incorrect, got 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' (see https://psalm.dev/011)

src/Model/Subscription.php:131:16: InvalidReturnStatement: The inferred type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' does not match the declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures (see https://psalm.dev/128)

Process completed with exit code 2.

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainType: Cannot resolve types for $this->lastRefreshOn with type DateTimeInterface and !isset assertion (see https://psalm.dev/056)

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainNull: Cannot resolve types for $this->lastRefreshOn - DateTimeInterface does not contain null (see https://psalm.dev/090)

src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php:24:5: MethodSignatureMismatch: Method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection::__construct has fewer parameters than parent method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\AbstractFeaturesCollection::__construct (see https://psalm.dev/042)

src/Model/Subscription.php:41:13: ParseError: Union types are not supported in PHP < 8 (see https://psalm.dev/173)

src/Model/Subscription.php:129:36: InvalidReturnType: The declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures is incorrect, got 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' (see https://psalm.dev/011)

src/Model/Subscription.php:131:16: InvalidReturnStatement: The inferred type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' does not match the declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures (see https://psalm.dev/128)

Process completed with exit code 2.

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainType: Cannot resolve types for $this->lastRefreshOn with type DateTimeInterface and !isset assertion (see https://psalm.dev/056)

src/Model/Feature/Subscribed/SubscribedCountableFeature.php:56:13: TypeDoesNotContainNull: Cannot resolve types for $this->lastRefreshOn - DateTimeInterface does not contain null (see https://psalm.dev/090)

src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php:24:5: MethodSignatureMismatch: Method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection::__construct has fewer parameters than parent method SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\AbstractFeaturesCollection::__construct (see https://psalm.dev/042)

src/Model/Subscription.php:41:13: ParseError: Union types are not supported in PHP < 8 (see https://psalm.dev/173)

src/Model/Subscription.php:129:36: InvalidReturnType: The declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures is incorrect, got 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' (see https://psalm.dev/011)

src/Model/Subscription.php:131:16: InvalidReturnStatement: The inferred type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection|array<array-key, mixed>|null' does not match the declared return type 'SerendipityHQ\Bundle\FeaturesBundle\Model\Feature\Subscribed\SubscribedFeaturesCollection' for SerendipityHQ\Bundle\FeaturesBundle\Model\Subscription::getFeatures (see https://psalm.dev/128)

Process completed with exit code 2.

Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires php ^8.0 but your php version (7.4.33) does not satisfy that requirement.