VarExporter Component

The VarExporter component provides various tools to deal with the internal state of objects:

• VarExporter::export() allows exporting any serializable PHP data structure to plain PHP code. While doing so, it preserves all the semantics associated with the serialization mechanism of PHP (__wakeup, __sleep, Serializable, __serialize, __unserialize);
• Instantiator::instantiate() creates an object and sets its properties without calling its constructor nor any other methods;
• Hydrator::hydrate() can set the properties of an existing object;
• Lazy*Trait can make a class behave as a lazy-loading ghost or virtual proxy.

VarExporter::export()

The reason to use VarExporter::export() vs serialize() or igbinary is performance: thanks to OPcache, the resulting code is significantly faster and more memory efficient than using unserialize() or igbinary_unserialize().

Unlike var_export(), this works on any serializable PHP value.

It also provides a few improvements over var_export()/serialize():

• the output is PSR-2 compatible;
• the output can be re-indented without messing up with \r or \n in the data;
• missing classes throw a ClassNotFoundException instead of being unserialized to PHP_Incomplete_Class objects;
• references involving SplObjectStorage, ArrayObject or ArrayIterator instances are preserved;
• Reflection*, IteratorIterator and RecursiveIteratorIterator classes throw an exception when being serialized (their unserialized version is broken anyway, see https://bugs.php.net/76737).

Instantiator and Hydrator

Instantiator::instantiate($class) creates an object of the given class without calling its constructor nor any other methods.

Hydrator::hydrate() sets the properties of an existing object, including private and protected ones. For example:

// Sets the public or protected $object->propertyName property
Hydrator::hydrate($object, ['propertyName' => $propertyValue]);

// Sets a private property defined on its parent Bar class:
Hydrator::hydrate($object, ["\0Bar\0privateBarProperty" => $propertyValue]);

// Alternative way to set the private $object->privateBarProperty property
Hydrator::hydrate($object, [], [
    Bar::class => ['privateBarProperty' => $propertyValue],
]);

Lazy Proxies

Since version 8.4, PHP provides support for lazy objects via the reflection API. This native API works with concrete classes. It doesn't with abstracts nor with internal ones.

This components provides helpers to generate lazy objects using the decorator pattern, which works with abstract or internal classes and with interfaces:

$proxyCode = ProxyHelper::generateLazyProxy(new ReflectionClass(AbstractFoo::class));
// $proxyCode should be dumped into a file in production envs
eval('class FooLazyProxy'.$proxyCode);

$foo = FooLazyProxy::createLazyProxy(initializer: function (): AbstractFoo {
    // [...] Use whatever heavy logic you need here
    // to compute the $dependencies of the $instance
    $instance = new Foo(...$dependencies);
    // [...] Call setters, etc. if needed

    return $instance;
});
// $foo is now a lazy-loading decorator object. The initializer will
// be called only when and if a *method* is called.

In addition, this component provides traits and methods to aid in implementing the ghost and proxy strategies in previous versions of PHP. Those are deprecated when using PHP 8.4.

Resources

• Documentation
• Contributing
• Report issues and send Pull Requests in the main Symfony repository