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phpbcmath

Bcmath adding decimal places randomly

I have a PHP function I got from the web that uses bcmath functions:

function SteamID64to32($steamId64) {
    $iServer = "1";
    if(bcmod($steamId64, "2") == "0") {
        $iServer = "0";
    }
    $steamId64 = bcsub($steamId64,$iServer);
    if(bccomp("76561197960265728",$steamId64) == -1) {
        $steamId64 = bcsub($steamId64,"76561197960265728");
    }
    $steamId64 = bcdiv($steamId64, "2");
    return ("STEAM_0:" . $iServer . ":" . $steamId64);
}

For any valid input the function will at random times add ".0000000000" to the output.

Ex:

$input = 76561198014791430;
SteamID64to32($input);

//result for each run
STEAM_0:0:27262851
STEAM_0:0:27262851.0000000000
STEAM_0:0:27262851
STEAM_0:0:27262851
STEAM_0:0:27262851.0000000000
STEAM_0:0:27262851
STEAM_0:0:27262851.0000000000
STEAM_0:0:27262851.0000000000
STEAM_0:0:27262851.0000000000

This was tested on 2 different nginx servers running php-fpm. Please help me understand what is wrong here. Thanks

Solution

  • The answer provided by JD doesn't account for all possible STEAM_ ID types, namely, anything that is in the STEAM_0:1 range. This block of code will:

    <?php

function Steam64ToSteam32($Steam64ID)
{
    $offset = $Steam64ID - 76561197960265728;
    $id = ($offset / 2);
    if($offset % 2 != 0)
    {
        $Steam32ID = 'STEAM_0:1:' . bcsub($id, '0.5');
    }
    else
    {
        $Steam32ID = "STEAM_0:0:" . $id;
    }
    return $Steam32ID;
}

echo Steam64ToSteam32(76561197960435530);
echo "<br/>";
echo Steam64ToSteam32(76561197990323733);
echo "<br/>";
echo Steam64ToSteam32(76561198014791430);
?>

    This outputs

    STEAM_0:0:84901
STEAM_0:1:15029002
STEAM_0:0:27262851

    The first one is for a Valve employee and someone who's had a Steam account since 2003 (hence the low ID), the second is a random profile I found on VACBanned which had an ID in the STEAM_0:1 range. The third is the ID you provided in your sample code.