Comments on: PHP vs. BIGINT vs. float conversion caveat

By: Skye

Skye — Thu, 24 Mar 2011 18:23:16 +0000

Good post. Saved me some headaches with large ints using sprintf.

By: SMAK

SMAK — Tue, 27 Jul 2010 08:25:24 +0000

Awesome, thanks you soo much for this post.

By: Kr±g Starszoharcerski “Matrix” » Blog Archive » Jak nie nale¿y obs³ugiwaæ du¿ych liczb

Wed, 23 Jan 2008 07:42:53 +0000

[...] przyk³ad – PHP. Ten akurat problem mnie za bardzo nie dotyczy³, ale to nie ¶wiadczy dobrze o PHP. Niestety, takich [...]

By: shodan

shodan — Sat, 12 Jan 2008 13:35:14 +0000

Pierre,
thanks for the link, but the post point is a bit different: it’s not about what you can use at this or that setup (there’s plenty of extensions); it’s only about the conversion issue you might run into.

By: Pierre

Pierre — Sat, 12 Jan 2008 09:24:24 +0000

Try http://pecl.php.net/package/big_int

It is relatively fast (given that you have a php function call on each op). About php and large integers, it never supported anything else than 32bits integer. Whether the integer was stored in the system default integer (64bits on amd64 for example) did not change this problem. It is annoying but once you know it

I have something about this topic on my todo, to expose the openssl math functions. They are not the faster on earth but they can then be available by default (as almost all setup has openssl installed).

By: Windows Update » Comment on PHP vs. BIGINT vs. float conversion caveat by Windows…

Sat, 12 Jan 2008 07:35:12 +0000

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By: Windows Update » PHP vs. BIGINT vs. float conversion caveat

Windows Update » PHP vs. BIGINT vs. float conversion caveat — Sat, 12 Jan 2008 03:25:08 +0000

[...] MySQL Performance Blog wrote an interesting post today on PHP vs. BIGINT vs. float conversion caveatHere’s a quick excerpt Sometimes you need to work with big numbers in PHP (gulp). For example, sometimes 32-bit identifiers are not enough and you have to use BIGINT 64-bit ids; e.g. if you are encoding additional information like the server ID into high bits of the ID. I had already written about the mess that 64-bit integers are in PHP. But if the numbers you use do not cover 64-bit range fully, floats might save the day. The trick is that PHP floats are in fact doubles, i.e. double-precision 64-bit numbers. They [...]

By: shodan

shodan — Fri, 11 Jan 2008 23:37:05 +0000

Jakub,

you were right, it’s the default settings of “precision” affecting this in ALL cases. Setting it to precision=16 (enough to hold 2^53 w/o sign) helps everywhere. The default values (both php.ini-dist and compiled-in) seems to vary but none of these reaches 16. I’ll update the post.

It’s not mentioned at php.net/float and the embedded description in php.ini-dist is, well, not quite clear (“The number of significant digits displayed in floating point numbers”). I believe it’s kept at default 12 as most if not all sites.

By: peter

peter — Fri, 11 Jan 2008 23:21:26 +0000

Antony,

Regarding other libraries to deal with big numbers in PHP they have one serious issue – they are rather slow.
Sometimes it does not matter but sometimes it does.

By: peter

peter — Fri, 11 Jan 2008 23:19:25 +0000

Thanks Andrew I’ve now modified the comment.