Base64 to Decimal

#!/usr/bin/php
<?php

/* Interpret Base64 encoded string as a binary number, 8 bits per character, MSB first
 * IN: Base64 encoded String
 * OUT: Decimal equivalent of string
 */

$in='';
while (!feof(STDIN))
{
    $res = fread(STDIN, 1024);
    if (false === $res)
    {
        fwrite(STDERR, "error reading from stdin");
        exit(3);
    }
    $in .= $res;
}

$result=base64_decode($in);
if (false===$result)
{
    fwrite(STDERR, "base64_decode failed");
    exit(3);
}

$gmp=gmp_import($result);
if (FALSE === $gmp) {
    fwrite(STDERR, "gmp_import failed");
    exit(3);
}

$result=gmp_strval($gmp, 10);
if (false===$result)
{
    fwrite(STDERR, "base64_encode failed");
    exit(3);
}

fwrite(STDOUT, $result);

exit(0);