Converting from any base number system to decimal (and back).

gistfile1.php

<?php

function toDecimal($base, $value)
{
    $value = (string) $value;

    $key   = array_flip(str_split($base));
    $base  = count($key);

    $parts = str_split($value);
    $steps = count($parts);
    $total = 0;

    for ($i = 0; $i < $steps; $i++)
    {
        $character = $parts[$i];
        $value     = $key[$parts[$i]];
        $power     = $steps - ($i + 1);
        $net       = (int) $value * pow($base, $power);

        $total += $net;
    }

    return $total;
}

function fromDecimal($base, $value)
{
    $points  = [];
    $values  = [];
    $value   = (string) $value;
    $numeric = (int) $value;
    $parts   = str_split($base);

    for ($i = 0; $i < 100; $i++)
    {
        array_unshift($points, pow(strlen($base), $i));
    }

    for ($i = 0; $i < 100; $i++)
    {
        $values[] = floor((float) bcdiv(sprintf("%.0f", $numeric), sprintf("%.0f", $points[$i])));
        $numeric  = (float) bcmod(sprintf("%.0f", $numeric), sprintf("%.0f", $points[$i]));
    }

    $values = array_map(function($value) use ($parts)
    {
        return $parts[$value];

    }, $values);

    return trim(join("", $values), $parts[0]);
}

// $base  = " abcdefghijklmnopqrstuvwxyz";
// $value = "hello world";

// echo "toDecimal: '" . toDecimal($base, $value) . "'\n";
// echo "fromDecimal: '" . fromDecimal($base, toDecimal($base, $value)) . "'\n";

// $base  = "01";
// $value = "10111001";

// echo "toDecimal: '" . toDecimal($base, $value) . "'\n";
// echo "fromDecimal: '" . fromDecimal($base, toDecimal($base, $value)) . "'\n";

// $base  = "0123456789";
// $value = "1337";

// echo "toDecimal: '" . toDecimal($base, $value) . "'\n";
// echo "fromDecimal: '" . fromDecimal($base, toDecimal($base, $value)) . "'\n";

$base  = "9876543210";
$value = "106212424";

echo "toDecimal: '" . toDecimal($base, $value) . "'\n";
echo "fromDecimal: '" . fromDecimal($base, toDecimal($base, $value)) . "'\n";