Get all permutations of a PHP array?

Question

Given a PHP array of strings, e.g.:

['peter', 'paul', 'mary'] 

How to generate all possible permutations of elements of this array? i.e.:

peter-paul-mary peter-mary-paul paul-peter-mary paul-mary-peter mary-peter-paul mary-paul-peter 

Answer 1

function pc_permute($items, $perms = array()) {     if (empty($items)) {          echo join(' ', $perms) . "<br />";     } else {         for ($i = count($items) - 1; $i >= 0; --$i) {              $newitems = $items;              $newperms = $perms;              list($foo) = array_splice($newitems, $i, 1);              array_unshift($newperms, $foo);              pc_permute($newitems, $newperms);          }     } }  $arr = array('peter', 'paul', 'mary');  pc_permute($arr); 

or

function pc_next_permutation($p, $size) {     // slide down the array looking for where we're smaller than the next guy     for ($i = $size - 1; $p[$i] >= $p[$i+1]; --$i) { }      // if this doesn't occur, we've finished our permutations     // the array is reversed: (1, 2, 3, 4) => (4, 3, 2, 1)     if ($i == -1) { return false; }      // slide down the array looking for a bigger number than what we found before     for ($j = $size; $p[$j] <= $p[$i]; --$j) { }      // swap them     $tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp;      // now reverse the elements in between by swapping the ends     for (++$i, $j = $size; $i < $j; ++$i, --$j) {          $tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp;     }      return $p; }  $set = split(' ', 'she sells seashells'); // like array('she', 'sells', 'seashells') $size = count($set) - 1; $perm = range(0, $size); $j = 0;  do {       foreach ($perm as $i) { $perms[$j][] = $set[$i]; } } while ($perm = pc_next_permutation($perm, $size) and ++$j);  foreach ($perms as $p) {     print join(' ', $p) . "\n"; } 

http://docstore.mik.ua/orelly/webprog/pcook/ch04_26.htm