Online PHP editor | refs for 2XYFM

<?php function is_cyclic(array &$array) { $lastKey = array_key_last($array); if ($lastKey === null) { // Array is empty return false; } static $marker; if ($marker === null) $marker = new stdClass(); if ($array[$lastKey] === $marker) { return true; } $array[] = $marker; foreach ($array as &$item) { if (is_array($item) && is_cyclic($item)) { array_pop($array); return true; } } array_pop($array); return false; } // Contains reference to itself $v = [1, 2, 3]; $v[1] = &$v; // Contains nested array with reference to $x $x = [1, [2, 3]]; $x[1][1] = &$x; // Contains nested array with reference to an ancestor $y = [1, [2, [3, 4]]]; $y[1][1][1] = &$y[1]; // Nested array contains reference to itself $z = [1, [2, 3]]; $z[1][1] = &$z[1]; // This array is not recursive $p = [1, 2, [3, 4, [5, 6, 7]]]; foreach (['v', 'x', 'y', 'z', 'p'] as $var) { $arr = &${$var}; echo "Array \$$var | Cyclic: "; var_export(is_cyclic($arr)); echo "\n"; echo "----------------\n"; var_dump($arr); echo "\n\n"; }