PHP's serialize() is slower than json_encode()

console.txt

Results:

json_encode: 14.230s | 392 Ko
serialize:   50.383s | 540 Ko
json_decode: 36.503s
unserialize: 40.666s

serialize_vs_json.php

<?php
date_default_timezone_set('Europe/Paris');

$dates = dates_for_period('-10 years', '+10 years');
$data  = array();
foreach($dates as $date)
{
  $year  = substr($date, 0, 4);
  $month = substr($date, 4, 2);
  $day   = substr($date, 6, 2);
  
  foreach(array('18-25', '26-35', '36-45', '46-55', '56-65', '66+') as $age) {
    $data[$age][$year][$month][$day] = rand(10, 1000);
  }
}

benchmark('json_encode', array($data), 1000);
benchmark('serialize', array($data), 1000);

benchmark('json_decode', array(json_encode($data), true), 1000);
benchmark('unserialize', array(serialize($data)), 1000);


function benchmark($func, $args, $times)
{
  $time = microtime(true);
  for ($i=0; $i<1000; $i++) {
    call_user_func_array($func, $args);
  }
  $time = microtime(true) - $time;
  
  $str = call_user_func_array($func, $args);
  if (is_string($str))
  {
    $size = strlen($str);
    printf("$func: %.3fs | %d Ko\n", $time, $size / 1024);
  }
  else {
    printf("$func: %.3fs\n", $time);
  }
}

function & dates_for_period($from, $to)
{
  $dates = array();
  $from  = strtotime($from);
  $to    = strtotime($to);
  $i     = 0;
  
  do
  {
    $time = strtotime("-{$i} day", $to);
    if ($time < $from) {
      break;
    }
    $dates[] = date('Ymd', $time);
    $i++;
  }
  while(true);
  
  sort($dates);
  return $dates;
}
?>