<?php

/**
 * [clean class]
 * 1.500   => 515.09 KB
 * 15.000  => 1.56 MB
 * 150.000 => 16.09 MB
 * 
 * [1 field]
 * 1.500   => 538.44 KB
 * 15.000  => 1.79 MB
 * 150.000 => 18.38 MB
 *
 * [3 field]
 * 1.500   => 597.52 KB
 * 15.000  => 2.37 MB
 * 150.000 => 24.1 MB
 */

final class CustomClass
{
    # private string $result = 'access';
    # private float $begin_time = 4738.994;
    # private float $run_time = 7264.544;
}

function memory_converter_to_string(int $size): string
{
    $unit = ['B', 'KB', 'MB', 'GB', 'TB', 'PB'];
    return round($size / pow(1024, ($i = floor(log($size, 1024)))), 2) . ' ' . $unit[$i];
}

$cached = array();

$begin = 0;
$limit = 1500;

for ($index = $begin; $index < $limit; $index++)
{
    $cached[$index] = new CustomClass();
}

echo memory_converter_to_string(memory_get_peak_usage()) . PHP_EOL;