WeakReferences
Among the many wonderful improvements coming in PHP 7.4, are WeakReferences. What is a weak reference? To answer that question, we first need to quickly skim how references work in PHP.
Strong references In PHP, objects are not stored in the variables they are assigned to. Instead, the variable stores a reference to that object. In this way, multiple variables can all point to the same object.
Up until now, all references used in PHP are implicitly strong references.