PHP base_convert to shorten urls

Question

I want my urls to be shorter, like tinyurl or any other short time. I have the following link types:

localhost/test/link.php?id=1000001
localhost/test/link.php?id=1000002

and etc.

The identifier in the links above is the auto-increment identifier of the rows from db. The above links are displayed as follows:

localhost/test/1000001
localhost/test/1000002

Now, instead of using the long identifiers described above, I would like to shorten them. I found that I can use the function base_convert(). For instance:

print base_convert(100000000, 10, 36);

//output will be "1njchs"

This looks good, but I want to ask if there is any drawback (for example, slow performance or whatever) of using this function, or is there any better approach to doing the same (for example, create your own function for generating random string IDs)?

Thank.

Answer 1

base_convert , , .

Answer 2

base_convert() intval()

: -

$code = base_convert("long string", 10, 36);
$ID= intval($code ,36); 

Answer 3

, base_convert(), . , , . , . , 256 ( ) base85 .

GMP

You can use GMP to accomplish this by converting bin ↔ hex two times unnecessarily, and is also limited by the base62.

<?php
// Not bits, bytes.
$data = openssl_random_pseudo_bytes(256);

$base62 = gmp_strval( gmp_init( bin2hex($data), 16), 62 );
$decoded = hex2bin( gmp_strval( gmp_init($base62, 62), 16 ));

var_dump( strcmp($decoded, $data) === 0 ); // true

Pure php

If you want to move beyond base62 to base85 or a slight performance improvement, you'll need something like the following.

<?php

/**
* Divide a large number represented as a binary string in the specified base
* and return the remainder.
* 
* @param string &$binary
* @param int $base
* @param int $start
*/
function divmod(&$binary, $base, $divisor, $start = 0)
{
    /** @var int $size */
    $size = strlen($binary);

    // Do long division from most to least significant byte, keep remainder.
    $remainder = 0;
    for ($i = $start; $i < $size; $i++) {
        // Get the byte value, 0-255 inclusive.
        $digit = ord($binary[$i]);

        // Shift the remainder left by base N bits, append the last byte.
        $temp = ($remainder * $base) + $digit;

        // Calculate the value for the current byte.
        $binary[$i] = chr($temp / $divisor);

        // Carry the remainder to the next byte.
        $remainder = $temp % $divisor;
    }

    return $remainder;
}

/**
* Produce a base62 encoded string from a large binary number.
* 
* @param string $binary
* return string
*/
function encodeBase62($binary)
{
    $charMap = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $base = strlen($charMap);

    $size = strlen($binary);
    $start = $size - strlen(ltrim($binary, "\0"));

    $encoded = "";
    for ($i = $start; $i < $size; ) {
        // Do long division from most to least significant byte, keep remainder.
        $idx = divmod($binary, 256, $base, $i);

        $encoded = $charMap[$idx] . $encoded;

        if (ord($binary[$i]) == 0) {
            $i++; // Skip leading zeros produced by the long division.
        }
    }

    $encoded = str_pad($encoded, $start, "0", STR_PAD_LEFT);

    return $encoded;
}

/**
* Produce a large binary number from a base62 encoded string.
* 
* @param string $ascii
* return string
*/
function decodeBase62($ascii)
{
    $charMap = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $base = strlen($charMap);

    $size = strlen($ascii);
    $start = $size - strlen(ltrim($ascii, "0"));

    // Convert the ascii representation to binary string.
    $binary = "";
    for ($i = $start; $i < $size; $i++) {
        $byte = strpos($charMap, $ascii[$i]);
        if ($byte === false) {
            throw new OutOfBoundsException("Invlaid encoding at offset '{$ascii[$i]}'");
        }

        $binary .= chr($byte);
    }

    $decode = "";
    for ($i = 0; $i < $size; ) {
        // Do long division from most to least significant byte, keep remainder.
        $idx = divmod($binary, $base, 256, $i);

        $decode = chr($idx) . $decode;

        if (ord($binary[$i]) == 0) {
            $i++; // Skip leading zeros produced by the long division.
        }
    }

    $decode = ltrim($decode, "\0");
    $decode = str_pad($decode, $start, "\0", STR_PAD_LEFT);

    return $decode;
}

// Not bits, bytes.
$data = openssl_random_pseudo_bytes(256);

$base62 = encodeBase62($data);
$decoded = decodeBase62($base62);

var_dump( strcmp($decoded, $data) === 0 ); // true