The clone
keyword is what you need.
$date2 = clone $date1;
When an object is cloned, a shallow copy of all of the object's properties. Any properties that are references to other variables, will remain references.
If your object $date2
holds a reference to another object $date1
which it uses and when you replicate the parent object you want to create a new instance of this other object so that the replica has its own separate copy.