string base64 to integer/float/char array in php

Question

I would like to convert a base64 string to other types, ie integer, float, and char array.

In Java I can use a ByteBuffer object, so it's easy to get values with methods like stream.getInt(), stream.getLong(), stream.getChar(), stream.getFloat(), etc.

But how to do this in PHP?

Edit: I tried the base64-decode PHP function, but this one decode a string, I want to decode numbers.

Edit2:

In Java:

import java.nio.ByteBuffer;
import javax.xml.bind.DatatypeConverter;

public class Main {

    public static void main(String[] args) {
        ByteBuffer stream = ByteBuffer.wrap(DatatypeConverter.parseBase64Binary("AAGdQw=="));
        while (stream.hasRemaining()) {
            System.out.println(stream.getInt());
        }
    }
}

displays 105795

But in php:

$nb = base64_decode('AAGdQw=='); // the result is not a stringified number, neither printable
settype($nb, 'int');
echo $nb;

displays 0, because base64_decode('AAGdQw==') is not printable.

have you tried anything so far? perhaps reading the manual, especially about base64_decode and type juggling? — Franz Gleichmann
– Franz Gleichmann, Commented Nov 18, 2016 at 10:22
Of course I tried base64_decode, but I don't want to decode a string, I want also to decode integers and floats. — roipoussiere
– roipoussiere, Commented Nov 18, 2016 at 10:23

Franz Gleichmann · Accepted Answer · 2016-11-18 13:26:25Z

4

you have to use unpack to convert the decoded string into a byte array, from which you then can reconstruct the integer:

<?php
$s = 'AAGdQw==';
$dec = base64_decode($s);
$ar = unpack("C*", $dec);
$i= ($ar[1]<<24) + ($ar[2]<<16) + ($ar[3]<<8) + $ar[4];

var_dump($i);
//output int(105795)

floats could be re-assembled with the pack-function, which creates a variable from a byte array.

but be advised that you have to take a lot of care about both data types AND the underlying hardware; especially the endianness (byte order) of the processor and the word size of the processor (32bit int differs from 64bit int) - therefore, if possible, you should use a text-based protocol, like JSON - which you can base64-encode, too.

answered Nov 18, 2016 at 13:26

Franz Gleichmann

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Community · Accepted Answer · 2023-11-17 20:18:34Z

0

Decode a content as is and cast a result to any type through type casting or some varialbe handling function such as settype().

If encoded file is large and you worried about memory consumption, you can use stream filters (relevant answer).

edited Nov 17, 2023 at 20:18

CommunityBot

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answered Nov 18, 2016 at 10:25

Timurib

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3 Comments

roipoussiere Over a year ago

Thank you. I tried but I don't understand why settype(base64_decode('AAGdQw=='), 'int') returns 1.

Timurib Over a year ago

settype() accepts argument by reference (see the manual), so you need to assign decoding result to a variable and apply settype. Also you can use intval().

roipoussiere Over a year ago

Works better. The fact is my base64 string do not contains a stringified integer, it contains the integer itself: ie AAGdQw== is supposed to be 105795, but the decoded string is not printable, so I don't think I can use it with intval(). See my edit.

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