<?php
// This is only an example, the numbers below will
// differ depending on your system

for ($i=1; $i<1000; $i++) {
  //echo "used memory is " . memory_get_usage() . "<br/>";
  $a = loadmem($i);
  //echo "used memory after allocating ".$i."m is " . memory_get_usage() . "<br/>"; // 57960
  //echo "used memory after unsetting allocated memory is " . memory_get_usage() . "<br/>"; // 36744
  echo '%' . $i . "\n";
  unset($a);
}

function loadmem($howmuchmeg) {
  $a = str_repeat("0", $howmuchmeg * 1024 * 1024); // alocating 10 chars times million chars
  return $a;
}

?>