CODEWITHSUNDEEP
php
gchimuel
gchimuel

Reputation: 527

How to convert byte array to integer in php?

I have seen a code that converts integer into byte array. Below is the code on How to convert integer to byte array in php 3 (How to convert integer to byte array in php):

<?php

$i = 123456;
$ar = unpack("C*", pack("L", $i));

print_r($ar);
?>

The above code will output:

//output:
Array
(
   [1] => 64
   [2] => 226
   [3] => 1
   [4] => 0
)

But my problem right now is how to reverse this process. Meaning converting from byte array into integer. In the case above, the output will be 123456

Can anybody help me with this. I would be a great help. Thanks ahead.

Upvotes: 8

Views: 12947

Answers (3)

ricozinn
ricozinn

Reputation: 131

In order to get a signed 4-byte value in PHP you need to do this:

    $temp = ($ar[0]<<24) + ($ar[1]<<16) + ($ar[2]<<8) + $ar[3];
    if($temp >= 2147483648)
         $temp -= 4294967296;

Upvotes: 4

PRB
PRB

Reputation: 484

Why not treat it like the math problem it is?

$i = ($ar[3]<<24) + ($ar[2]<<16) + ($ar[1]<<8) + $ar[0];

Upvotes: 11

Niet the Dark Absol
Niet the Dark Absol

Reputation: 324630

Since L is four bytes long, you know the number of elements of the array. Therefore you can simply perform the operation is reverse:

$ar = [64,226,1,0];
$i = unpack("L",pack("C*",$ar[3],$ar[2],$ar[1],$ar[0]));

Upvotes: 5

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