Loading CS2D map in PHP

<?php
function ReadByte($file) {
    return unpack("C", fgets($file,2))[1];
}

function ReadInt($file) {
    return unpack("i", fgets($file,5))[1];
}

function ReadString($file) {
    return trim(fgets($file));
}

$map = "de_cs2d";
$file = fopen("$map.map", "r");

// Header
$header = ReadString($file);
if ($header != "Unreal Software's Counter-Strike 2D Map File (max)") {
    exit("The header is not supported\n");
}

// 10 bytes for map settings
ReadByte($file);
$modifiers = ReadByte($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);

// 10 ints for map settings
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);
ReadInt($file);

// 10 strings for map settings
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);
ReadString($file);

// More map settings
ReadString($file);
ReadString($file);
$tiles = ReadByte($file);
$map_xsize = ReadInt($file);
$map_ysize = ReadInt($file);
ReadString($file);
ReadInt($file);
ReadInt($file);
ReadByte($file);
ReadByte($file);
ReadByte($file);

// Header Test
$test = ReadString($file);
if ($test != "ed.erawtfoslaernu") {
    exit("The header is corrupted\n");
}

// Tile Modes
for ($i = 0; $i <= $tiles; $i++) {
    $mode = ReadByte($file);
    echo "$i = $mode\n";
}

// Map
for ($x = 0; $x <= $map_xsize; $x++) {
    for ($y = 0; $y <= $map_ysize; $y++) {
        $tile = ReadByte($file);
        echo "$x|$y = $tile\n";
    }
}

// Modifiers
if ($modifiers == 1) {
    exit("The modifiers are not supported\n");
}

// Entities
$entity_count = ReadInt($file);
for ($j = 1; $j <= $entity_count; $j++) {
    ReadString($file);
    $entity_type = ReadByte($file);
    $entity_x = ReadInt($file);
    $entity_y = ReadInt($file);
    ReadString($file);
    echo "$entity_x|$entity_y = $entity_type\n";

    for ($k = 1; $k <= 10; $k++) {
        ReadInt($file);
        ReadString($file);
    }
}

// End of file
fclose($file);
?>