The VarExporter Component
Edit this pageThe VarExporter Component
The VarExporter component exports any serializable PHP data structure to plain PHP code and allows to instantiate and populate objects without calling their constructors.
Installation
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$ composer require --dev symfony/var-exporterNote
If you install this component outside of a Symfony application, you must
require the vendor/autoload.php file in your code to enable the class
autoloading mechanism provided by Composer. Read
this article for more details.
Exporting/Serializing Variables
The main feature of this component is to serialize PHP data structures to plain PHP code, similar to PHP's var_export function:
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use Symfony\Component\VarExporter\VarExporter;
$exported = VarExporter::export($someVariable);
// store the $exported data in some file or cache system for later reuse
$data = file_put_contents('exported.php', '<?php return '.$exported.';');
// later, regenerate the original variable when you need it
$regeneratedVariable = require 'exported.php';The reason to use this component instead of serialize() or igbinary is
performance: thanks to OPcache, the resulting code is significantly faster
and more memory efficient than using unserialize() or igbinary_unserialize().
In addition, there are some minor differences:
- If the original variable defines them, all the semantics associated with
serialize()(such as__wakeup(),__sleep(), andSerializable) are preserved (var_export()ignores them); - References involving
SplObjectStorage,ArrayObjectorArrayIteratorinstances are preserved; - Missing classes throw a
ClassNotFoundExceptioninstead of being unserialized toPHP_Incomplete_Classobjects; Reflection*,IteratorIteratorandRecursiveIteratorIteratorclasses throw an exception when being serialized.
The exported data is a PSR-2 compatible PHP file. Consider for example the following class hierarchy:
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abstract class AbstractClass
{
protected $foo;
private $bar;
protected function setBar($bar)
{
$this->bar = $bar;
}
}
class ConcreteClass extends AbstractClass
{
public function __construct()
{
$this->foo = 123;
$this->setBar(234);
}
}When exporting the ConcreteClass data with VarExporter, the generated PHP
file looks like this:
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<?php
return \Symfony\Component\VarExporter\Internal\Hydrator::hydrate(
$o = [
clone (\Symfony\Component\VarExporter\Internal\Registry::$prototypes['Symfony\\Component\\VarExporter\\Tests\\ConcreteClass'] ?? \Symfony\Component\VarExporter\Internal\Registry::p('Symfony\\Component\\VarExporter\\Tests\\ConcreteClass')),
],
null,
[
'Symfony\\Component\\VarExporter\\Tests\\AbstractClass' => [
'foo' => [
123,
],
'bar' => [
234,
],
],
],
$o[0],
[]
);Instantiating PHP Classes
The other main feature provided by this component is an instantiator which can create objects and set their properties without calling their constructors or any other methods:
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use Symfony\Component\VarExporter\Instantiator;
// creates an empty instance of Foo
$fooObject = Instantiator::instantiate(Foo::class);
// creates a Foo instance and sets one of its properties
$fooObject = Instantiator::instantiate(Foo::class, ['propertyName' => $propertyValue]);
// creates a Foo instance and sets a private property defined on its parent Bar class
$fooObject = Instantiator::instantiate(Foo::class, [], [
Bar::class => ['privateBarProperty' => $propertyValue],
]);Instances of ArrayObject, ArrayIterator and SplObjectHash can be
created by using the special "\0" property name to define their internal value:
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// Creates an SplObjectHash where $info1 is associated with $object1, etc.
$theObject = Instantiator::instantiate(SplObjectStorage::class, [
"\0" => [$object1, $info1, $object2, $info2...],
]);
// creates an ArrayObject populated with $inputArray
$theObject = Instantiator::instantiate(ArrayObject::class, [
"\0" => [$inputArray],
]);
