How to cast a 32-bit integer from unsigned to signed in MySQL or PHP?
Question
I have a string in PHP (came from some data source), which represents a formatted unsigned 32-bit integer. I need to store it into a MySQL database as a signed 32-bit integer, so that later I can retrieve it from PHP and use it as a (possibly negative) signed integer constant (since PHP doesn't have unsigned integers).
So, what I need is a conversion method, either for PHP or MySQL. It shouldn't be platform-dependent (no endian / 32/64-bit issues).
I know how to convert a signed integer into unsigned using MySQL:
select CAST((-1062726980 & 0xFFFFFFFF) AS UNSIGNED INTEGER);
+------------------------------------------------------+
| CAST((-1062726980 & 0xFFFFFFFF) AS UNSIGNED INTEGER) |
+------------------------------------------------------+
| 3232240316 |
+------------------------------------------------------+
But I can't get it work the other way around (note: MySQL uses 64-bit arithmetic when doing casts).
Thanks.
Solution 2
This:
$val = (bccomp("2147483647", $val) < 0) ? bcsub($val, "4294967296") : $val;
seems to work, even though it's somewhat slow.
OTHER TIPS
If you just cast the number to an integer in PHP, it will do the trick.
echo (int)3232240316 . "\n";
gives
-1062726980
Note: if you want to cast a signed int to an unsigned int in PHP, just do this:
$number += 4294967296;
Example:
$number = -1062726980;
echo $number . "\n";
$number += 4294967296;
echo $number . "\n";
gives:
-1062726980
3232240316