base62_convert.php

base62_convert.php

/**
 * Convert a numeric string from base 10 to another base.
 *
 * @param $value  decimal string
 * @param int $b  base , max is 62
 * @return string
 */
function to_base($value, $b = 62)
{
    $base = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $r = $value  % $b;
    $result = $base[$r];
    $q = floor($value / $b);

    while ($q)
    {
        $r = $q % $b;
        $q = floor($q / $b);
        $result = $base[$r].$result;
    }

    return $result;
}



/**
 * Convert a string from a given base to base 10.
 *
 * @param  string  $value  string from given base
 * @param  int     $b      base, max is 62
 * @return string
 */
function to_base10($value, $b = 62)
{
    $base = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $limit = strlen($value);
    $result = strpos($base, $value[0]);

    for($i = 1; $i < $limit; $i++)
    {
        $result = $b * $result + strpos($base, $value[$i]);
    }

    return $result;
}



/**
 * Convert a 10 base numeric string to a 62 base string
 *
 * @param  int     $value
 * @return string
 */
function base62_encode($value)
{
    return to_base($value, 62);
}


/**
 * Convert a string from base 62 to base 10 numeric string
 *
 * @param  string     $value
 * @return int
 */
function base62_decode($value)
{
    return to_base10($value, 62);
}