day6.php

<?php
$l = str_repeat('0', 1000000);
$i = file('i');

foreach ($i as $s) {
        $tok = strtok($s, ' ');
        $instruction = 1;
        $c = '';
        if ($tok === 'toggle') {
                $instruction = 0;
        } else {
                if (strtok(' ') === 'on') {
                        $c = '1';
                } else {
                        $c = '0';
                }
        }

        $x = strtok(',');
        $y = strtok(' ');
        strtok(' ');
        $d = strtok(',');
        $e = strtok("\n");

        while ($x <= $d) {
                $z = $y;
                while ($z <= $e) {
                        $a = $l[$x + $z * 1000];
                        if ($instruction === 0) {
                                $c = $a === '1' ? '0' : '1';
                        }

                        $l[$x + $z * 1000] = $c;

                        $z += 1;
                }

                $x += 1;
        }
}

echo substr_count($l, '1');