PHP: Converting big integer from string to int with overflow

Question

PHP does not support unsigned ints. Is there a way to convert a string representation of an unsigned integer into a signed integer with overflow?

Example:
On a 32 bit system, PHP can store int values <= 2147483647. I want a way to convert the string "2147483648" to integer, causing it to overflow to -2147483648 instead of being reduced to 2147483647.

Why do I want to do this?
I store IPv4 addresses in a database as unsigned int (32 bits). I want to do binary operations on the addresses in PHP to check for subnets. This needs to be done on every request, so it needs to be quick. Therefore it seems better to store the IP address as an unsigned int rather than storing a string which will have to be converted back and forth.

Yes, assuming I will always be in control of the environment where the application is deployed. I don't know if this will always be the case. — MW.
– MW., Commented Oct 28, 2011 at 10:36

Emir Akaydın · Accepted Answer · 2011-10-28 11:12:03Z

4

here is the workaround.

<?php
    $unsignedString = "3000000000";
    echo "unsigned string: ".$unsignedString."<br />";
    $signedInt = intval(doubleval($unsignedString));
    echo "signed int: ".$signedInt."<br />";
?>

edited Oct 28, 2011 at 11:12

answered Oct 28, 2011 at 11:06

Emir Akaydın

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Comments

Hammerite · Accepted Answer · 2011-10-28 11:05:23Z

0

The fastest and easiest way to do this is to get your RDBMS to do it somehow.

You can find out what the size of an integer is in PHP by checking the value of the predefined constant PHP_INT_SIZE. This will be 4 if running on a 32-bit system, 8 if running on a 64-bit system.

I suggest that you populate a variable with for example

$smallIntegers = intval(PHP_INT_SIZE == 4);

and then in your query use something like this:

SELECT
    ...,
    CASE
        WHEN :smallIntegers: = 1 AND IPAddress > 2147483647 THEN IPAddress - 4294967296
        ELSE IPAddress
    END AS IPAddress,
    ...
...

answered Oct 28, 2011 at 11:05

Hammerite

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1 Comment

MW. Over a year ago

As you say, this would probably be faster, but I would like to do it in PHP in order to preserve my architecture.

Kasheen · Accepted Answer · 2011-10-28 11:08:10Z

0

Could you store the IP address in an integer array, one segment of the IP to each part of the array so the max value would end up as 255 stored in anyone one integer:

$ipAddress = array(127, 0, 0, 1);

answered Oct 28, 2011 at 11:08

Kasheen

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1 Comment

MW. Over a year ago

I'm afraid not - this would sort of defeat the purpose of being able to use bitwise operations on the address.

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