Array vs SplFixedArray: memory usage simple

array_vs_splfixedarray_memory_usage_simple.php

<?php

$sizes = [];
for ($exp = 0; $exp < 20; $exp++) {
    $size = pow(2, $exp);
    if ($size < 1000) {
        continue;
    }
    
    $sizes[] = $size - ($size / 4);
    $sizes[] = $size - ($size / 8);
    $sizes[] = $size - ($size / 16);
    $sizes[] = $size;
    $sizes[] = $size + ($size / 16);
    $sizes[] = $size + ($size / 8);
    $sizes[] = $size + ($size / 4);
}

echo "size, memoryArray (KB), memorySpl (KB)" . PHP_EOL;

foreach ($sizes as $size) {
    $startMemory = memory_get_usage();
    $array = createOrdinaryArray($size);
    $stopMemoryOrdinary = round((memory_get_usage() - $startMemory) / 1024, 2);
    unset($array);
    
    
    $startMemory = memory_get_usage();
    $array = createSplArray($size);
    $stopMemorySpl = round((memory_get_usage() - $startMemory) / 1024, 2);
    unset($array);
    
    echo "{$size}, {$stopMemoryOrdinary}, {$stopMemorySpl}" . PHP_EOL;
}

function createOrdinaryArray(int $size): array
{
    $array = [];
    for ($i = 0; $i < $size; $i++) {
        $array[$i] = null;
    }
    
    return $array;
}

function createSplArray(int $size): SplFixedArray
{
    $array = new SplFixedArray($size);
    for ($i = 0; $i < $size; $i++) {
        $array[$i] = null;
    }
    
    return $array;
}

Result: https://docs.google.com/spreadsheets/d/1CvYtz40_HWFU_1ZMbzQQM5hykwD7hXPz8joTC8tCKgQ/edit#gid=1231078169