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  1. <?php
  2.  
  3. $recursive = array(42);
  4. $recursive['recursive'] = &$recursive;
  5.  
  6. $deepRecursive = array(42);
  7. $deepRecursive['this']['recursion']['happens']['deeper'] = $recursive; // just for fun
  8.  
  9. $nonrec = array(42);
  10. $nonrec[] = $nonrec; // not recursive, this is a static copy of the array
  11.  
  12.  
  13. echo "Recursive:      ".(int)is_recursive($recursive)."\n";
  14. echo "Deep recursive: ".(int)is_recursive($deepRecursive)."\n";
  15. echo "Non-recursive:  ".(int)is_recursive($nonrec)."\n";
  16.  
  17. function is_recursive(array &$array, array &$alreadySeen = array()) {
  18.     static $uniqueObject;
  19.     if (!$uniqueObject) {
  20.         $uniqueObject = new stdClass;
  21.     }
  22.  
  23.     $alreadySeen[] = &$array;
  24.  
  25.     foreach ($array as &$item) {
  26.         if (!is_array($item)) {
  27.             continue;
  28.         }
  29.  
  30.         $item[] = $uniqueObject;
  31.         $recursionDetected = false;
  32.         foreach ($alreadySeen as $candidate) {
  33.             if (end($candidate) === $uniqueObject) {
  34.                 $recursionDetected = true;
  35.                 break;
  36.             }
  37.         }
  38.  
  39.         array_pop($item);
  40.  
  41.         if ($recursionDetected || is_recursive($item, $alreadySeen)) {
  42.             return true;
  43.         }
  44.     }
  45.  
  46.     return false;
  47. }
  48.  
Success #stdin #stdout 0.01s 20568KB
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Standard input is empty
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Recursive:      1
Deep recursive: 1
Non-recursive:  0
https://ideone.com/2IQwpQ
language:
PHP (php 7.3.5)
created:
12 years ago
visibility:
public

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