Recursive Array

A recursive array is an array that contains a reference to itself. It is a legit construction, although it introduces a loop, between an element and the original variable. This has impact on traversing the array, in particular to count or to compare the array.

<?php
    $a = [1, 2, 3 => &$a];

    print_r($a);

    /**
    Array
(
    [0] => 1
    [1] => 2
    [3] => Array
 *RECURSION*
)
*/
?>

Related : References, Array, Recursion