UPGRADE FROM 4.2 to 4.3

BrowserKit

Renamed Client to AbstractBrowser
Marked Response final.
Deprecated Response::buildHeader()
Deprecated Response::getStatus(), use Response::getStatusCode() instead

Cache

The psr/simple-cache dependency has been removed - run composer require psr/simple-cache if you need it.
Deprecated all PSR-16 adapters, use Psr16Cache or Symfony\Contracts\Cache\CacheInterface implementations instead.
Deprecated SimpleCacheAdapter, use `Psr16Adapter instead.

Config

Deprecated using environment variables with cannotBeEmpty() if the value is validated with validate()

Form

Using the format option of DateType and DateTimeType when the html5 option is enabled is deprecated.
Using names for buttons that do not start with a letter, a digit, or an underscore is deprecated and will lead to an exception in 5.0.
Using names for buttons that do not contain only letters, digits, underscores, hyphens, and colons is deprecated and will lead to an exception in 5.0.
Using the date_format, date_widget, and time_widget options of the DateTimeType when the widget option is set to single_text is deprecated.

FrameworkBundle

Not passing the project directory to the constructor of the AssetsInstallCommand is deprecated. This argument will be mandatory in 5.0.
Deprecated the "Psr\SimpleCache\CacheInterface" / "cache.app.simple" service, use "Symfony\Contracts\Cache\CacheInterface" / "cache.app" instead.
The generate() method of the UrlGenerator class can return an empty string instead of null.

HttpFoundation

The MimeTypeGuesserInterface and ExtensionGuesserInterface interfaces have been deprecated, use Symfony\Component\Mime\MimeTypesInterface instead.
The MimeType and MimeTypeExtensionGuesser classes have been deprecated, use Symfony\Component\Mime\MimeTypes instead.
The FileBinaryMimeTypeGuesser class has been deprecated, use Symfony\Component\Mime\FileBinaryMimeTypeGuesser instead.
The FileinfoMimeTypeGuesser class has been deprecated, use Symfony\Component\Mime\FileinfoMimeTypeGuesser instead.

HttpKernel

renamed Client to HttpKernelBrowser

Messenger

Amqp transport does not throw \AMQPException anymore, catch TransportException instead.

Routing

The generator_base_class, generator_cache_class, matcher_base_class, and matcher_cache_class router options have been deprecated.
Implementing Serializable for Route and CompiledRoute is deprecated; if you serialize them, please ensure your unserialization logic can recover from a failure related to an updated serialization format

Security

The Role and SwitchUserRole classes are deprecated and will be removed in 5.0. Use strings for roles instead.
The RoleHierarchyInterface is deprecated and will be removed in 5.0.
The getReachableRoles() method of the RoleHierarchy class is deprecated and will be removed in 5.0. Use the getReachableRoleNames() method instead.
The getRoles() method of the TokenInterface is deprecated. Tokens must implement the getRoleNames() method instead and return roles as strings.

The AbstractToken::serialize(), AbstractToken::unserialize(), AuthenticationException::serialize() and AuthenticationException::unserialize() methods are now final, use getState() and setState() instead.

Before:

public function serialize()
{
    return [$this->myLocalVar, parent::serialize()];
}

public function unserialize($serialized)
{
    [$this->myLocalVar, $parentSerialized] = unserialize($serialized);
    parent::unserialize($parentSerialized);
}

After:

protected function getState(): array
{
    return [$this->myLocalVar, parent::getState()];
}

protected function setState(array $data)
{
    [$this->myLocalVar, $parentData] = $data;
    parent::setState($parentData);
}

Yaml

Using a mapping inside a multi-line string is deprecated and will throw a ParseException in 5.0.

Uh oh!