UPGRADE FROM 3.x to 4.0

ClassLoader

The ApcClassLoader, WinCacheClassLoader and XcacheClassLoader classes have been removed in favor of the --apcu-autoloader option introduced in composer 1.3

Console

Setting unknown style options is not supported anymore and throws an exception.

Debug

FlattenException::getTrace() now returns additional type descriptions integer and float.

DependencyInjection

Service identifiers are now case sensitive.
The Reference and Alias classes do not make service identifiers lowercase anymore.
Using the PhpDumper with an uncompiled ContainerBuilder is not supported anymore.
The DefinitionDecorator class has been removed. Use the ChildDefinition class instead.
Using unsupported configuration keys in YAML configuration files raises an exception.
Using unsupported options to configure service aliases raises an exception.
Setting or unsetting a private service with the Container::set() method is no longer supported. Only public services can be set or unset.
Checking the existence of a private service with the Container::has() method is no longer supported and will return false.
Requesting a private service with the Container::get() method is no longer supported.

EventDispatcher

The ContainerAwareEventDispatcher class has been removed. Use EventDispatcher with closure-proxy injection instead.

ExpressionLanguage

The ability to pass a ParserCacheInterface instance to the ExpressionLanguage class has been removed. You should use the CacheItemPoolInterface interface instead.

Finder

The ExceptionInterface has been removed.

Form

The choices_as_values option of the ChoiceType has been removed.
Support for data objects that implements both Traversable and ArrayAccess in ResizeFormListener::preSubmit method has been removed.

Using callable strings as choice options in ChoiceType is not supported anymore in favor of passing PropertyPath instances.

Before:

'choice_value' => new PropertyPath('range'),
'choice_label' => 'strtoupper',

After:

'choice_value' => 'range',
'choice_label' => function ($choice) {
    return strtoupper($choice);
},

Caching of the loaded ChoiceListInterface in the LazyChoiceList has been removed, it must be cached in the ChoiceLoaderInterface implementation instead.
Calling isValid() on a Form instance before submitting it is not supported anymore and raises an exception.

Before:
```
if ($form->isValid()) {
    // ...
}
```
After:
```
if ($form->isSubmitted() && $form->isValid()) {
    // ...
}
```

FrameworkBundle

Support for absolute template paths has been removed.
The following form types registered as services have been removed; use their fully-qualified class name instead:
- "form.type.birthday"
- "form.type.checkbox"
- "form.type.collection"
- "form.type.country"
- "form.type.currency"
- "form.type.date"
- "form.type.datetime"
- "form.type.email"
- "form.type.file"
- "form.type.hidden"
- "form.type.integer"
- "form.type.language"
- "form.type.locale"
- "form.type.money"
- "form.type.number"
- "form.type.password"
- "form.type.percent"
- "form.type.radio"
- "form.type.range"
- "form.type.repeated"
- "form.type.search"
- "form.type.textarea"
- "form.type.text"
- "form.type.time"
- "form.type.timezone"
- "form.type.url"
- "form.type.button"
- "form.type.submit"
- "form.type.reset"
The framework.serializer.cache option and the services serializer.mapping.cache.apc and serializer.mapping.cache.doctrine.apc have been removed. APCu should now be automatically used when available.
The Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\AddConsoleCommandPass has been removed. Use Symfony\Component\Console\DependencyInjection\AddConsoleCommandPass instead.

SecurityBundle

The FirewallContext::getContext() method has been removed, use the getListeners() method instead.

HttpFoundation

Extending the following methods of Response is no longer possible (these methods are now final):
- setDate/getDate
- setExpires/getExpires
- setLastModified/getLastModified
- setProtocolVersion/getProtocolVersion
- setStatusCode/getStatusCode
- setCharset/getCharset
- setPrivate/setPublic
- getAge
- getMaxAge/setMaxAge
- setSharedMaxAge
- getTtl/setTtl
- setClientTtl
- getEtag/setEtag
- hasVary/getVary/setVary
- isInvalid/isSuccessful/isRedirection/isClientError/isServerError
- isOk/isForbidden/isNotFound/isRedirect/isEmpty
The ability to check only for cacheable HTTP methods using Request::isMethodSafe() is not supported anymore, use Request::isMethodCacheable() instead.

HttpKernel

Possibility to pass non-scalar values as URI attributes to the ESI and SSI renderers has been removed. The inline fragment renderer should be used with non-scalar attributes.
The ControllerResolver::getArguments() method has been removed. If you have your own ControllerResolverInterface implementation, you should inject an ArgumentResolverInterface instance.
The DataCollector::varToString() method has been removed in favor of cloneVar().
The Psr6CacheClearer::addPool() method has been removed. Pass an array of pools indexed by name to the constructor instead.

Security

The RoleInterface has been removed. Extend the Symfony\Component\Security\Core\Role\Role class instead.

Serializer

The ability to pass a Doctrine Cache instance to the ClassMetadataFactory class has been removed. You should use the CacheClassMetadataFactory class instead.
Not defining the 6th argument $format = null of the AbstractNormalizer::instantiateObject() method when overriding it is not supported anymore.

Translation

Removed the backup feature from the file dumper classes.

TwigBridge

Removed the possibility to inject the Form TwigRenderer into the FormExtension. Upgrade Twig to ^1.30, inject the Twig_Environment into the TwigRendererEngine and load the TwigRenderer using the Twig_FactoryRuntimeLoader instead.

Before:

use Symfony\Bridge\Twig\Extension\FormExtension;
use Symfony\Bridge\Twig\Form\TwigRenderer;
use Symfony\Bridge\Twig\Form\TwigRendererEngine;

// ...
$rendererEngine = new TwigRendererEngine(array('form_div_layout.html.twig'));
$rendererEngine->setEnvironment($twig);
$twig->addExtension(new FormExtension(new TwigRenderer($rendererEngine, $csrfTokenManager)));

After:

$rendererEngine = new TwigRendererEngine(array('form_div_layout.html.twig'), $twig);
$twig->addRuntimeLoader(new \Twig_FactoryRuntimeLoader(array(
    TwigRenderer::class => function () use ($rendererEngine, $csrfTokenManager) {
        return new TwigRenderer($rendererEngine, $csrfTokenManager);
    },
)));
$twig->addExtension(new FormExtension());

Removed the TwigRendererEngineInterface interface.
The TwigRendererEngine::setEnvironment() method has been removed. Pass the Twig Environment as second argument of the constructor instead.

Validator

The DateTimeValidator::PATTERN constant was removed.

Tests\Constraints\AbstractConstraintValidatorTest has been removed in favor of Test\ConstraintValidatorTestCase.

Before:

// ...
use Symfony\Component\Validator\Tests\Constraints\AbstractConstraintValidatorTest;

class MyCustomValidatorTest extends AbstractConstraintValidatorTest
{
    // ...
}

After:

// ...
use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;

class MyCustomValidatorTest extends ConstraintValidatorTestCase
{
    // ...
}

The default value of the strict option of the Choice Constraint has been changed to true as of 4.0. If you need the previous behaviour ensure to set the option to false.

Yaml

Mappings with a colon (:) that is not followed by a whitespace are not supported anymore and lead to a ParseException(e.g. foo:bar must be foo: bar).
Starting an unquoted string with % leads to a ParseException.
The Dumper::setIndentation() method was removed. Pass the indentation level to the constructor instead.
Removed support for passing true/false as the second argument to the parse() method to trigger exceptions when an invalid type was passed.

Before:
```
Yaml::parse('{ "foo": "bar", "fiz": "cat" }', true);
```
After:
```
Yaml::parse('{ "foo": "bar", "fiz": "cat" }', Yaml::PARSE_EXCEPTION_ON_INVALID_TYPE);
```

Removed support for passing true/false as the third argument to the parse() method to toggle object support.

Before:

Yaml::parse('{ "foo": "bar", "fiz": "cat" }', false, true);

After:

Yaml::parse('{ "foo": "bar", "fiz": "cat" }', Yaml::PARSE_OBJECT);

Removed support for passing true/false as the fourth argument to the parse() method to parse objects as maps.

Before:

Yaml::parse('{ "foo": "bar", "fiz": "cat" }', false, false, true);

After:

Yaml::parse('{ "foo": "bar", "fiz": "cat" }', Yaml::PARSE_OBJECT_FOR_MAP);

Removed support for passing true/false as the fourth argument to the dump() method to trigger exceptions when an invalid type was passed.

Before:

Yaml::dump(array('foo' => new A(), 'bar' => 1), 0, 0, true);

After:

Yaml::dump(array('foo' => new A(), 'bar' => 1), 0, 0, Yaml::DUMP_EXCEPTION_ON_INVALID_TYPE);

Removed support for passing true/false as the fifth argument to the dump() method to toggle object support.

Before:

Yaml::dump(array('foo' => new A(), 'bar' => 1), 0, 0, false, true);

After:

Yaml::dump(array('foo' => new A(), 'bar' => 1), 0, 0, false, Yaml::DUMP_OBJECT);

The !!php/object tag to indicate dumped PHP objects was removed in favor of the !php/object tag.
Duplicate mapping keys lead to a ParseException.

Uh oh!