Add DeepClone to Data Structure and Storage

README.md

@@ -747,6 +747,7 @@ Please see [CONTRIBUTING](https://github.com/ziadoz/awesome-php/blob/master/CONT
 *Libraries that implement data structure or storage techniques.*
 
 * [CakePHP Collection](https://github.com/cakephp/collection) - A simple collections library.
+* [DeepClone](https://github.com/symfony/php-ext-deepclone) - A PHP extension to export serializable values as plain arrays and reconstruct them.
 * [Fractal](https://github.com/thephpleague/fractal) - A library for converting complex data structures to JSON output.
 * [JsonMapper](https://github.com/cweiske/jsonmapper) - A library that maps nested JSON structures onto PHP classes.
 * [JSON Machine](https://github.com/halaxa/json-machine) - Provides iteration over huge JSONs using simple `foreach`.