binary-trees PHP program

<?php 
/* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

   contributed by Peter Baltruschat
   modified by Levi Cameron
   *reset*
*/

class Node {
	public $l;
	public $r;
}

function bottomUpTree($depth)
{
   $node = new Node();
   if (!$depth) return $node;
   $depth--;
   $node->l = bottomUpTree($depth);
   $node->r = bottomUpTree($depth);
   return $node;
}

function itemCheck($treeNode) { 
   return 1
      + ($treeNode->l->l === null ? 1 : itemCheck($treeNode->l))
      + ($treeNode->r->l === null ? 1 : itemCheck($treeNode->r));
}

$minDepth = 4;

$n = ($argc == 2) ? $argv[1] : 1;
$maxDepth = max($minDepth + 2, $n);
$stretchDepth = $maxDepth + 1;

$stretchTree = bottomUpTree($stretchDepth);
printf("stretch tree of depth %d\t check: %d\n", $stretchDepth, itemCheck($stretchTree));
unset($stretchTree);

$longLivedTree = bottomUpTree($maxDepth);

$iterations = 1 << ($maxDepth);
do
{
   $check = 0;
   for($i = 1; $i <= $iterations; ++$i)
   {
      $t = bottomUpTree($minDepth);
      $check += itemCheck($t);
      unset($t);
   }
   
   printf("%d\t trees of depth %d\t check: %d\n", $iterations, $minDepth, $check);
   
   $minDepth += 2;
   $iterations >>= 2;
}
while($minDepth <= $maxDepth);

printf("long lived tree of depth %d\t check: %d\n",
$maxDepth, itemCheck($longLivedTree));

    

NOTES:
64-bit Ubuntu quad core
PHP 8.3.11 (cli)
(built: Sep  5 2024 12:34:23) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.3.11,
with Zend OPcache v8.3.11,
Copyright (c) Zend Technologies


 Thu, 05 Sep 2024 20:09:39 GMT

COMMAND LINE:
 /opt/src/php-8.3.11/bin/php -dzend_extension=/opt/src/php-8.3.11/lib/php/extensions/no-debug-non-zts-20230831/opcache.so -dopcache.enable_cli=1 -dopcache.jit_buffer_size=64M -n -d memory_limit=4096M binarytrees.php 21

PROGRAM OUTPUT:
stretch tree of depth 22	 check: 8388607
2097152	 trees of depth 4	 check: 65011712
524288	 trees of depth 6	 check: 66584576
131072	 trees of depth 8	 check: 66977792
32768	 trees of depth 10	 check: 67076096
8192	 trees of depth 12	 check: 67100672
2048	 trees of depth 14	 check: 67106816
512	 trees of depth 16	 check: 67108352
128	 trees of depth 18	 check: 67108736
32	 trees of depth 20	 check: 67108832
long lived tree of depth 21	 check: 4194303