Daniel Gomes, a developer at Teamleader, explains a potential problem when cloning object in PHP.

As you know, PHP has a well-known clone keyword that shallow copy all of the object’s properties. So under the hood what it does is to create a new Object with the exact same values of that object properties – unless you change its behavior by implementing the clone() function in your class.

https://dcsg.me/articles/dont-clone-your-php-objects-deepcopy-them/