Convert Large Integer to Hexadecimal without PHP Math extension

PHP has a couple of functions to convert integers to hexadecimal, dechex() and base_convert(). However, both functions lose precision on large integers.

For example:

[code language=“php“]
$bigint_hash = ‚11442725345190069619‘;
$hexadecimal_hash = ‚9eccba134669c573‘;
$converted_hash = dechex( $bigint_hash+0 ); //+0 just makes sure a float is passed to function
echo ‚Decimal value is: ‚. $bigint_hash. "/n";
echo ‚Hexidecimal value SHOULD be : ‚. $hexadecimal_hash. "/n";
echo ‚Hexidecimal value converts to: ‚. $converted_hash. "/n";

//outputs
/*
Decimal value is: 11442725345190069619
Hexidecimal value SHOULD be : 9eccba134669c573
Hexidecimal value converts to: 9eccba134669c800
*/
[/code]

There are PHP solutions that allow you to create an alternative to dechex() / base_convert( $num, 16, 10 ) with more accuracy but they require BC Math or GMP extensions to be installed.

A colleague of mine passed on an alternative to dechex() or base_convert( $num, 16, 10 ) that was apparently listed on php.net but was removed due (I’m guessing!) to some bad language filter despite how semantically accurate the function’s naming convention uses.

Here it is:

[code language=“php“]
/* Follows the syntax of base_convert (http://www.php.net/base_convert)
* Created by Michael Renner @ http://www.php.net/base_convert 17-May-2006 03:24
* His comment is has since been deleted. The function will tell you why.
*/
function unfucked_base_convert($numstring, $frombase, $tobase)
{

$chars = "0123456789abcdefghijklmnopqrstuvwxyz";
$tostring = substr($chars, 0, $tobase);

$length = strlen($numstring);
$result = “;
for ($i = 0; $i < $length; $i++)
{
$number[$i] = strpos($chars, $numstring{$i});
}
do
{
$divide = 0;
$newlen = 0;
for ($i = 0; $i < $length; $i++)
{
$divide = $divide * $frombase + $number[$i];
if ($divide >= $tobase)
{
$number[$newlen++] = (int)($divide / $tobase);
$divide = $divide % $tobase;
} elseif ($newlen > 0)
{
$number[$newlen++] = 0;
}
}
$length = $newlen;
$result = $tostring{$divide} . $result;
} while ($newlen != 0);
return $result;
}
[/code]

The source can be found on GitHub.

Now I can convert with freedom:

[code language=“php“]
$bigint_hash = ‚11442725345190069619‘;
$hexadecimal_hash = ‚9eccba134669c573‘;
$converted_hash = unfucked_base_convert( $bigint_hash, 16, 10 );
echo ‚Decimal value is: ‚. $bigint_hash. "/n";
echo ‚Hexidecimal value SHOULD be : ‚. $hexadecimal_hash. "/n";
echo ‚Hexidecimal value converts to: ‚. $converted_hash. "/n";

//outputs
/*
Decimal value is: 11442725345190069619
Hexidecimal value SHOULD be : 9eccba134669c573
Hexidecimal value converts to: 9eccba134669c573
*/
[/code]