PHP memory leak

memleak.php

<?php
function printMemoryUsage() {
    gc_collect_cycles();
    printf("Memory used: %.4fMB\n", memory_get_usage() / 1024 / 1024);
}

gc_enable();

$batchCount = 1000;
$iterations = 10000;

class Container {
    private $data;

    public function __construct(array $data)
    {
        $this->data = $data;
    }

    public function getData()
    {
        $data = $this->data;
        // trigger copy-on-write again.
        $data[2] = 'write';
        return $data;
    }
}

$data = range(0, 10);

$output = [];

printMemoryUsage();
echo "--Doing array usage...";

printMemoryUsage();

/**
 * Iterating using only arrays
 */
for ($i = 0; $i < $iterations; $i++) {
    $item = $data;
    // trigger copy-on-write
    $item[1] = 'write';

    $output[] = $item;

    if ($i && !($i % $batchCount)) {
        printMemoryUsage();
    }
}
$output = [];
$item = null;
echo "--Reset after array usage\n";
printMemoryUsage();

/**
 * Iterating using objects
 */
for ($i = 0; $i < $iterations; $i++) {
    $item = $data;
    // trigger copy-on-write
    $item[1] = 'write';

    $instance = new Container($item);
    $output[] = $instance->getData();

    if ($i && !($i % $batchCount)) {
        $instance = null;
        printMemoryUsage();
    }
}
$output = [];
$item = null;
$instance = null;
echo "--Reset after object usage\n";

printMemoryUsage();