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);
• DeepCloner deep-clones PHP values while preserving copy-on-write benefits for strings and arrays, making it faster and more memory efficient than unserialize(serialize());
• Lazy*Trait can make a class behave as a lazy-loading ghost or virtual proxy.

The component depends on the native ext-deepclone extension for maximum performance, or on its polyfill as a fallback. In addition to functions deepclone_to_array() and deepclone_from_array() which are leveraged by DeepCloner and VarExporter::export(), the extension provides a deepclone_hydrate() function that lets you instantiate / hydrate objects without calling their constructor, including private, protected and readonly properties.

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).

DeepCloner

DeepCloner::deepClone() deep-clones a PHP value. Unlike unserialize(serialize()), it preserves PHP's copy-on-write semantics for strings and arrays, resulting in lower memory usage and better performance:

$clone = DeepCloner::deepClone($originalObject);

For repeated cloning of the same structure, create an instance to amortize the cost of graph analysis:

$cloner = new DeepCloner($prototype);
$clone1 = $cloner->clone();
$clone2 = $cloner->clone();

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.

Resources

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