
<?php

$iter = 1000;

$time = microtime(true);
for ($i = 0; $i < $iter; $i++) {
  // noop
}
$baseline = microtime(true) - $time; 

$results = array();

for ($i = 0; $i < $iter; $i++) {

  $data = md5(mt_rand());;

  foreach (array('md5', 'sha1', 'sha256', 'sha512') as $algo) {
    $time = microtime(true);
    for ($j = 0; $j < $iter; $j++) {
      $h = hash($algo, $data, true);
    }
    $results[$algo][] = (microtime(true) - $time - $baseline) * 1000000 / $iter;
  }
}
$averages = array();
$stdev = array();

foreach ($results as $algo => $res) {
  $averages[$algo] = 0;

  foreach ($res as $time) {
    $averages[$algo] += $time;
  }
  $averages[$algo] /= (count($res));
}

foreach ($results as $algo => $res) { 
  $stdev[$algo] = 0;

  foreach ($res as $time) {
    $stdev[$algo] += pow($time - $averages[$algo], 2);
  }
  $stdev[$algo] = sqrt($stdev[$algo]/(count($res) -1));
}


echo PHP_EOL . PHP_EOL . 'Results: ' . PHP_EOL;

$i = 1;
foreach ($results as $algo => $v) {
  echo "$algo:  {$averages[$algo]} +/- {$stdev[$algo]} microseconds for $iter 32 byte values $iter times each\n";
}