Test array vs fixed array memory usage

index.php

<?php
$limit = 100000;

$arr1 = array();
for ($i = 0; $i < $limit; $i++) {
    $arr1[$i] = rand(1, $limit);
}

$startMemoryUsage = memory_get_usage();
$arr2 = array();
foreach ($arr1 as $key => $value) {
    $arr2[$key] = $value;
}
$memReg = (memory_get_usage() - $startMemoryUsage);
print 'Mem usage: ' . $memReg . PHP_EOL;
unset($arr2);

$startMemoryUsage = memory_get_usage();
$arr3 = new splFixedArray($limit);
foreach ($arr1 as $key => $value) {
    $arr3[$key] = $value;
}
$memImp = (memory_get_usage() - $startMemoryUsage);
print 'Mem usage: ' . $memImp . PHP_EOL;
print 'Mem gain: ' . number_format($memReg / $memImp, 2) . ' for ' . number_format($limit) . ' records';
unset($arr3);