fannkuch-redux PHP program

<? /* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
   
   contributed by Isaac Gouy, transliterated from Mike Pall's Lua program 
*/

function Fannkuch($n){
   $p = $q = $s = array(); 
   $sign = 1; $maxflips = $sum = 0; $m = $n-1;
   for ($i=0; $i<$n; $i++){ $p[$i] = $i; $q[$i] = $i; $s[$i] = $i; }      
   do {
      // Copy and flip.
      $q0 = $p[0];                                          // Cache 0th element.
      if ($q0 != 0){
         for($i=1; $i<$n; $i++) $q[$i] = $p[$i];            // Work on a copy.
         $flips = 1;
         do { 
            $qq = $q[$q0]; 
            if ($qq == 0){                                  // ... until 0th element is 0.
               $sum += $sign*$flips;
	       if ($flips > $maxflips) $maxflips = $flips;  // New maximum?
               break; 
            } 
 	    $q[$q0] = $q0; 
	    if ($q0 >= 3){
	       $i = 1; $j = $q0 - 1;
               do { $t = $q[$i]; $q[$i] = $q[$j]; $q[$j] = $t; $i++; $j--; } while ($i < $j); 
            }
	    $q0 = $qq; $flips++;
         } while (true); 
      }
      // Permute.
      if ($sign == 1){
         $t = $p[1]; $p[1] = $p[0]; $p[0] = $t; $sign = -1; // Rotate 0<-1.
      } else { 
         $t = $p[1]; $p[1] = $p[2]; $p[2] = $t; $sign = 1;  // Rotate 0<-1 and 0<-1<-2.
         for($i=2; $i<$n; $i++){ 
	    $sx = $s[$i];
	    if ($sx != 0){ $s[$i] = $sx-1; break; }
	    if ($i == $m) return array($sum,$maxflips);     // Out of permutations.
	    $s[$i] = $i;
	    // Rotate 0<-...<-i+1.
	    $t = $p[0]; for($j=0; $j<=$i; $j++){ $p[$j] = $p[$j+1]; } $p[$i+1] = $t;
         }
      }
   } while (true);
}

$n = $argv[1];
list($checksum,$pf) = Fannkuch($n);
printf("%d\nPfannkuchen(%d) = %d", $checksum, $n, $pf);
?>

    

NOTES:
64-bit Ubuntu quad core
PHP 7.4.5 (cli) (built: May 11 2020 13:25:48) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies


Mon, 11 May 2020 20:58:37 GMT

COMMAND LINE:
/opt/src/php-7.4.5/bin/php -n  fannkuchredux.php 12

PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65