Re: is_numeric_string causes function inconsistency

[Apologies for having accidentally responded to Matt W off-list, and now bringing it back on-list without asking...] On Sat, August 12, 2006 2:50 am, Matt W wrote: > From: "Richard Lynch" > Sent: Friday, August 11, 2006 > > >> Leading whitespace in PHP means that it's not a number, it's a >> string, >> and it turns into 0. >> >> If you change that, it will break a lot of stuff. >> >> Don't. >> >> :-) > > This is basically what Jochem Mass said, and my reply was: > > "Leading whitespace is already allowed with PHP's is_numeric() > function (and > corresponding internal one), math operations, etc. Only when it > precedes > .123 or -.123 does the behavior change. :-)" > > So with math operations, leading whitespace doesn't cause it (an > otherwise > numeric-prefix string) to turn into 0 (and never has), unless the > first > character(s) after the whitespace are "." or "-." Changing this > specific > (and rarely, if ever, occuring) scenario shouldn't break stuff... but > merely > make it operate the way it should. :-) But I think you are talking about making changes to the way this works: http://example.com/?foo=%20.123 <?php $foo = $_GET['foo']; if (is_numeric($foo)){ //error out } $query = "something involving '$foo'"; ?> If you break that, you're in big trouble to a lot of scripts all over the planet, which rely on the leading space to trap their SQL problem. I never actually use is_numeric, and would expect it to follow the same "rules" as PHP's internal type-juggling mechanism. I believe leading spaces should NOT be allowed for type-juggling, not is_numeric, because GET/POST/COOKIE data should be subject to the most stringent constraints reasonable to avoid security injections. I really think the community is best served by K.I.S.S. which means is_numeric should follow the same "rules" as type-juggling, so that the programmer is not confused by which does what, and that those rules for what constitutes is_numeric() should not have leading (or trailing) spaces. There is also a paradigm of only specifically allowing what "should be" valid for a validity/security check on data constraints. While I don't think leading/trailing spaces are likely to constitute a Security Issue, there is a Principle at work that I think should be applied. Surely is_numeric(trim($foo)) is the right answer for the programmer who specifically wants to allow spaces. The fact that PHP even allows leading spaces for this is what I would consider a bug: <?php $foo = ' 123'; $bar = (int) $foo; echo "bar: $bar"; ?> EXPECTED OUTPUT: bar: ACTUAL OUTPUT: bar: 123 I understand the argument that this buggy behaviour is inconsistent with ' .123' and ' -.123' but would counter that the bug is in allowing the leading spaces, and is not best addressed by making it consistently buggy. jmho -- Like Music? http://l-i-e.com/artists.htm