<?php

$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$coordinates = $coordinatesPrint = [];
$folds       = [];

foreach ($input as $line) {
    if (strstr($line, 'fold')) {
        preg_match('#fold along ([x|y])=(\d*)#', $line, $found);
        $folds[] = [$found[1], (int)$found[2]];
    } else {
        $point         = explode(',', $line);
        $coordinates[] = $point;
    }
}

foreach ($folds as $fold) {
    foreach ($coordinates as &$point) {
        if ($fold[0] == 'x' && $point[0] > $fold[1]) {
            $point[0] = $fold[1] * 2 - $point[0];
        }
        if ($fold[0] == 'y' && $point[1] > $fold[1]) {
            $point[1] = $fold[1] * 2 - $point[1];
        }
    }
    $coordinates = points_unique($coordinates);
}

printImage($coordinates); // PGHRKLKL


function points_unique($coordinates)
{
    $tmp            = [];
    $newCoordinates = [];
    foreach ($coordinates as $point) {
        if (!isset($tmp[implode(',', $point)])) {
            $newCoordinates[]          = $point;
            $tmp[implode(',', $point)] = 1;
        }
    }
    return $newCoordinates;
}

function printImage($coordinates)
{
    $maxx = $maxy = 0;
    foreach ($coordinates as $point) {
        if ($point[0] > $maxx) {
            $maxx = $point[0];
        }
        if ($point[1] > $maxy) {
            $maxy = $point[1];
        }
    }
    $image = array_fill(0, $maxy + 1, array_fill(0, $maxx + 1, ' '));
    foreach ($coordinates as $point) {
        $image[$point[1]][$point[0]] = '#';
    }
    echo implode("\n", array_map(fn($line) => implode('', $line), $image));
}