nbt.php

<?php
define('NBT_END', 0);
define('NBT_BYTE', 1);
define('NBT_SHORT', 2);
define('NBT_INT', 3);
define('NBT_LONG', 4);
define('NBT_FLOAT', 5);
define('NBT_DOUBLE', 6);
define('NBT_BYTE_ARRAY', 7);
define('NBT_STRING', 8);
define('NBT_LIST', 9);
define('NBT_COMPOUND', 10);
define('NBT_INT_ARRAY', 11);

function nbt_readTag($f) {
    return unpack('C', fread($f, 1))[1];
}

function nbt_readString($f) {
    $len = unpack('n', fread($f, 2))[1];
    if($len > 0) {
        return utf8_decode(fread($f, $len));
    } else {
        return '';
    }
}

function nbt_readCompound($f) {
    $compound = [];

    $next = nbt_readTag($f);
    while($next != NBT_END) {
        $name = nbt_readString($f);
        $compound[$name] = nbt_readDynamic($f, $next);

        $next = nbt_readTag($f);
    }

    return $compound;
}

function nbt_readList($f) {
    $list = [];
    $tag = nbt_readTag($f);
    $len = unpack('N', fread($f, 4))[1];

    for($i = 0; $i < $len; $i++) {
        $list[$i] = nbt_readDynamic($f, $tag);
    }

    return $list;
}

function signedInt16($s) {
    if($s >= 0x8000) {
        return -1 - ($s & 0x7FFF);
    } else {
        return $s;
    }
}

function signedInt32($i) {
    if($i >= 0x80000000) {
        return -1 - ($i & 0x7FFFFFFF);
    } else {
        return $i;
    }
}

function signedInt64($l) {
    if($l >= 0x8000000000000000) {
        return -1 - ($l & 0x7FFFFFFFFFFFFFFF);
    } else {
        return $l;
    }
}

function nbt_readDynamic($f, $tag) {
    switch($tag) {
    case NBT_BYTE:
        return unpack('c', fread($f, 1))[1];

    case NBT_SHORT:
        return signedInt16(unpack('n', fread($f, 2))[1]);

    case NBT_INT:
        return signedInt32(unpack('N', fread($f, 4))[1]);

    case NBT_LONG:
        $l = (unpack('N', fread($f, 4))[1] * 0x100000000) + (int)unpack('N', fread($f, 4))[1];
        return signedInt64($l);

    case NBT_FLOAT:
        return unpack('f', strrev(fread($f, 4)))[1];

    case NBT_DOUBLE:
        return unpack('d', strrev(fread($f, 8)))[1];

    case NBT_BYTE_ARRAY:
        $len = unpack('N', fread($f, 4))[1];
        fread($f, $len); //discard
        return '(BYTE_ARRAY)';

    case NBT_STRING:
        return nbt_readString($f);

    case NBT_LIST:
        return nbt_readList($f);

    case NBT_COMPOUND:
        return nbt_readCompound($f);

    case NBT_INT_ARRAY:
        $len = unpack('N', fread($f, 4))[1];
        fread($f, 4 * $len); //discard
        return '(INT_ARRAY)';
    }
}

/* NBT reader */
function nbtdecode($nbt) {
    $f = fopen('php://memory', 'r+');
    fwrite($f, $nbt);
    rewind($f);

    $result = FALSE;

    $tag = nbt_readTag($f);
    if($tag == NBT_COMPOUND) {
        nbt_readString($f); //discard name
        $result = nbt_readCompound($f);
    } else {
        die('top level needs to be a compound');
    }

    fclose($f);
    return $result;
}
?>