Bug #74748 [Opn->Nab]: HexDec outputs invalid conversions

Edit report at https://bugs.php.net/bug.php?id=74748&edit=1 ID: 74748 Updated by: danack@php.net Reported by: sysop at pkx dot pw Summary: HexDec outputs invalid conversions -Status: Open +Status: Not a bug Type: Bug Package: Math related Operating System: LInux Mint 18 PHP Version: Irrelevant Block user comment: N Private report: N New Comment: You are converting decimal to hex, which converts the number to the representation, but doesn't save the signed information. $hexed = dechex(-9223372036854775805); var_dump($hexed); var_dump(dechex(PHP_INT_MAX)); //Output is string(16) "8000000000000003" string(16) "7fffffffffffffff" When PHP goes to convert back from this string, to a decimal, it interprets 0x80000000003 as an unsigned number. As that number is bigger than PHP_INT_MAX, it overflows to a floating point number, where weird things start happening, as not every int can be represented in a float above 2**53. Perhaps you want to be using the pack and unpack functions: http://php.net/manual/en/function.pack.php http://php.net/manual/en/function.unpack.php Which shouldn't make assumptions about the signedness of numbers. Previous Comments: ------------------------------------------------------------------------ [2017-06-12 08:38:46] sysop at pkx dot pw Description: ------------ --- From manual page: http://www.php.net/function.hexdec --- Test script: --------------- var_dump((int)hexdec(dechex(-9223372036854775805))); var_dump((int)hexdec(dechex(-9223372036854775804))); var_dump((int)hexdec(dechex(-9223372036854775803))); Expected result: ---------------- int(-9223372036854775808) int(-9223372036854775808) int(-9223372036854775808) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=74748&edit=1