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Re: Rejecting Certain Non-ASCII Characters [message #181165 is a reply to message #181155]

Fri, 19 April 2013 20:33

Thomas 'PointedEars'
Messages: 701
Registered: October 2010

Karma:

Senior Member

Christoph Becker wrote:

> Jim Higgins wrote:
>> I have a problem with people entering a slashed zero vs a standard
>> ASCII zero into HTML forms intended to store data in a MySQL database.
>
> Is it really a slashed zero (U+0030 U+0338) they're entering,

Could also be U+0030 U+337 or any other (allowed composition) of the at
least 65536 Unicode characters that look(s) similar. For example, it could
be U+2205 EMPTY SET.

> or do they enter some similar looking character such as the Danish Ø?

That character, U+00D8 LATIN CAPITAL LETTER O WITH STROKE *and* its
lowercase counterpart, U+00F8 LATIN SMALL LETTER O WITH STROKE, are present
at least in Danish, Norwegian, and Faroese; They are also used in the
International Phonetic Alphabet (IPA).

> In the former case you can simply replace the slashed zero with a standard
> zero. Assuming UTF-8 encoding:
>
> $input = str_replace('\xCC\xB8', '', $input);

You do not consider that, ambiguity aside, even in UTF-8 there are *several*
ways to produce Unicode characters. See: Unicode Normalization Forms.

>> Is there a simple way in PHP to restrict input to the ASCII Character
>> set, specifically hex 0x20 - 0x7E ? Or a simple way to detect
>> characters outside this range before committing them to the database?
>
> If you're dealing with a numeric column, you may consider checking for
> is_numeric().

There are also regular expressions. Testing against '/[^\0x00-\x7F]/', and
rejecting anything that matches, appears to be the best approach here. If
characters actually should be converted, iconv() should be used instead of a
hardcoded conversion.

However, it is better in the long term to convert the MySQL database (or the
relevant table and column) to utf8_general_ci, and upgrade MySQL if
necessary (character sets and collations were not supported before MySQL 5;
the current stable version is 5.6).

<http://php.net/pcre>
<http://dev.mysql.com/>

PointedEars
--
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
-- Richard Cornford, cljs, <f806at$ail$1$8300dec7(at)news(dot)demon(dot)co(dot)uk>

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[Message index]

		Rejecting Certain Non-ASCII Characters By: Jim Higgins on Fri, 19 April 2013 16:16
		Re: Rejecting Certain Non-ASCII Characters By: Lew Pitcher on Fri, 19 April 2013 16:29
		Re: Rejecting Certain Non-ASCII Characters By: Daniel Pitts on Fri, 19 April 2013 16:30
		Re: Rejecting Certain Non-ASCII Characters By: Jim Higgins on Fri, 19 April 2013 21:38
		Re: Rejecting Certain Non-ASCII Characters By: Jim Higgins on Fri, 19 April 2013 22:11
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Fri, 19 April 2013 16:48
		Re: Rejecting Certain Non-ASCII Characters By: Jim Higgins on Fri, 19 April 2013 21:46
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Fri, 19 April 2013 22:00
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Fri, 19 April 2013 23:23
		Re: Rejecting Certain Non-ASCII Characters By: Christoph Becker on Fri, 19 April 2013 17:38
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Fri, 19 April 2013 20:33
		Re: Rejecting Certain Non-ASCII Characters By: Christoph Becker on Fri, 19 April 2013 21:08
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Fri, 19 April 2013 23:12
		Re: Rejecting Certain Non-ASCII Characters By: Christoph Becker on Mon, 22 April 2013 11:25
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Mon, 22 April 2013 11:29
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Sat, 20 April 2013 12:08
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Sat, 20 April 2013 15:52
		Re: Rejecting Certain Non-ASCII Characters By: Jim Higgins on Fri, 19 April 2013 22:06
		Re: Rejecting Certain Non-ASCII Characters By: Christoph Becker on Fri, 19 April 2013 22:26
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Fri, 19 April 2013 23:53
		Re: Rejecting Certain Non-ASCII Characters By: Christoph Becker on Sat, 20 April 2013 00:36
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sat, 20 April 2013 00:58
		Re: Rejecting Certain Non-ASCII Characters By: Christoph Becker on Sat, 20 April 2013 01:34
		Re: Rejecting Certain Non-ASCII Characters By: Arno Welzel on Fri, 19 April 2013 20:19
		Re: Rejecting Certain Non-ASCII Characters By: M. Strobel on Sat, 20 April 2013 08:04
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Sat, 20 April 2013 12:15
		Re: Rejecting Certain Non-ASCII Characters By: M. Strobel on Sat, 20 April 2013 12:26
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Sat, 20 April 2013 12:34
		Re: Rejecting Certain Non-ASCII Characters By: Arno Welzel on Sat, 20 April 2013 12:41
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sat, 20 April 2013 12:43
		Re: Rejecting Certain Non-ASCII Characters By: Arno Welzel on Sat, 20 April 2013 12:55
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sat, 20 April 2013 13:04
		Re: Rejecting Certain Non-ASCII Characters By: Arno Welzel on Sat, 20 April 2013 19:29
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sun, 21 April 2013 00:03
		Re: Rejecting Certain Non-ASCII Characters By: Arno Welzel on Sun, 21 April 2013 04:51
		Re: Rejecting Certain Non-ASCII Characters By: Arno Welzel on Sun, 21 April 2013 04:57
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sun, 21 April 2013 12:45
		Re: Rejecting Certain Non-ASCII Characters By: Tim Streater on Sun, 21 April 2013 14:09
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sun, 21 April 2013 14:29
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sun, 21 April 2013 12:44
		Re: Rejecting Certain Non-ASCII Characters By: The Natural Philosoph on Sat, 20 April 2013 14:07
		Re: Rejecting Certain Non-ASCII Characters By: Jerry Stuckle on Sun, 21 April 2013 00:06
		Re: Rejecting Certain Non-ASCII Characters By: M. Strobel on Sat, 20 April 2013 15:43
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Sat, 20 April 2013 16:01
		Re: Rejecting Certain Non-ASCII Characters By: M. Strobel on Sat, 20 April 2013 16:17
		Address munging (was: Rejecting Certain Non-ASCII Characters) By: Thomas 'PointedEars' on Sat, 20 April 2013 16:23
		OT: Address munging (was: Re: Rejecting Certain Non-ASCII Characters) By: Arno Welzel on Sat, 20 April 2013 19:25
		Re: Rejecting Certain Non-ASCII Characters By: Denis McMahon on Sat, 20 April 2013 22:06
		Re: Rejecting Certain Non-ASCII Characters By: Thomas 'PointedEars' on Mon, 22 April 2013 12:10

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