gistfile1.txt

ckwalsh@ckwalsh:~$ cat a.php 
<?php

class FooBar {
  public static function run() {
    $start = memory_get_usage(true);
    $j = 500000;
    for ($i = 0; $i < $j; $i++) {
      $Store[] = array($i, rand(0,50000000));
    }
    var_dump(memory_get_usage(true) - $start);
  }
}

FooBar::run();
ckwalsh@ckwalsh:~$ php a.php 
int(292552704)
ckwalsh@ckwalsh:~$ hhvm a.php 
int(36587312)
ckwalsh@ckwalsh:~$