1.2.320. Cyclic References

Avoid cyclic references.

Cyclic references happen when an object points to another object, which reciprocate. This is particularly possible with classes, when the child class has to keep a reference to the parent class. Cyclic references, or circular references, are memory intensive : only the garbage collector can understand when they may be flushed from memory, which is a costly operation. On the other hand, in an acyclic reference code, the reference counter will know immediately know that an object is free or not.

<?php

class a {
    private $p = null;

    function foo() {
        $this->p = new b();
        // the current class is stored in the child class
        $this->p->m($this);
    }
}

class b {
    private $pb = null;

    function n($a) {
        // the current class keeps a link to its parent
        $this->pb = $a;
    }
}
?>

See also About circular references in PHP and A Journey to find a memory leak.

1.2.320.1. Suggestions

• Use a different object when calling the child objects.

• Refactor your code to avoid the cyclic reference.

1.2.320.2. Specs

Short name	Classes/CyclicReferences
Rulesets	All, Analyze, Class Review
Exakat since	2.1.3
PHP Version	All
Severity	Minor
Time To Fix	Quick (30 mins)
Precision	Very high
Features	class, extends
Available in	Entreprise Edition, Exakat Cloud