base64 encoding of binary value of 64 bit integer in PHP is not working

How to use base64 encoding with binary string of 64 bit integer on PHP?

This code is not working as expected

<?PHP
$t=11545152599186258990;
$byte_array_t = pack('P',$t);
echo base64_encode($byte_array_t); //not correct result - it should be: LrwswB6fOKA=
echo '
';
$t=11;
$byte_array_t = pack('P',$t);
echo base64_encode($byte_array_t); //correct

I am doing this because I am trying to implement the below code (golang) in PHP:

package main
import (
"fmt"
"encoding/base64"
"encoding/binary"
)



func main()  {

    dst := make([]byte, 8)
    binary.LittleEndian.PutUint64(dst, uint64(11545152599186258990))
    value :=base64.URLEncoding.EncodeToString(dst)
    fmt.Println(value)



}

Update

Try using gmp_export instead of pack. Make sure to pass the integer as a string to gmp_init since it will overflow otherwise:

$t = gmp_init("11545152599186258990");
$byte_array_t = gmp_export($t, 8);
echo base64_encode($byte_array_t); // LrwswB6fOKA=

Demo

I suggest a tricky solution for you, divide your number into two 32Bit and Pack them.

$value = 11545152599186258990;
$highMap = 0xffffffff00000000; 
$lowMap = 0x00000000ffffffff; 
$higher = ($value & $highMap) >>32; 
$lower = $value & $lowMap; 
$packed = pack('NN', $higher, $lower); 

list($higher, $lower) = array_values(unpack('N2', $packed)); 
$originalValue = $higher << 32 | $lower; 

• Algorithm is taken from http://php.net/pack#109328

First thanks to JimB for his right comment and Regarding your question in comments ,

> Is there any way to get the binary value of 11545152599186258990 in PHP?

The answer is :

> PHP internally stores integer values as signed values of a machine-dependent size (C type long). Integer literals and operations that yield numbers outside the bounds of the integer type will be stored as float. When packing these floats as integers, they are first cast into the integer type. This may or may not result in the desired byte pattern. http://php.net/manual/ro/function.pack.php

And the Range of inputs on 64-bit machines is

> 9223372036854775807 (largest signed integer) http://php.net/manual/en/function.decbin.php

And you can compare it with your given Number .

There is very important topic here https://wiki.php.net/rfc/pack_unpack_64bit_formats and finally here https://github.com/php/php-src/commit/63fd969300e39302b1f8c600bc24f049a0e13370

but is still within the limit of largest signed integer.