Circular references: weak references

weak-references.php

<?php

class ParentClass
{
    public function __construct()
    {
        $this->child = new ChildClass($this);
    }
}

class ChildClass
{
    public function __construct(ParentClass $parent)
    {
        $this->parent = new WeakRef($parent);
    }
}

$instance = new ParentClass;

// Do your work...

// Once the parent instance is unreferenced, the parent and child instances will be destroyed.
unset($instance);