I have function that sanitizes URLs and filenames and it works fine with characters like éáßöäü as it replaces them with eassoau etc. using str_replace($a, $b, $value). But how can I replace all characters from Chinese, Japanese … languages? And if replacing is not possible because it's not easy to determine, how can I remove all those characters? Of course I could first sanitize it like above and then remove all "non-latin" characters. But maybe there is another good solution to that?
Edit/addition
As asked in the comments: What is the purpose of my question? We had a client that had content in English, German and Russian language at first. Later on there came some chinese pages. Two problems occurred with the URLs:
the first sanitizer killed all 'non-ascii-characters' and possibly returned 'blank' (invalid) clean-URLs
the client experienced that in some Browser clean URLs with Chinese characters wouldn't work
The first point led me to the shot to replace those characters, which is of course, as stated in the question and the comments confirmed it, not possible. Maybe now somebody is answering that in all modern browsers (starting with IE8) this ain't an issue anymore. I would also be glad to hear about that too.
As for Japanese, as an example, there is usually a romanji representation of everything which uses only ascii characters and still gives a reversable and understandable representation of the original characters. However translating something into romanji requires that you know the correct pronounciation, and that usually depends on the meaning or the context in which the characters are used. That makes it hard if not impossible to simply convert everything correcly (or at least not efficiently doable for a simple sanitizer).
The same applies to Chinese, in an even worse way. Korean on the other hand has a very simple character set which should be easily translateable into a roman representation. Another common problem though is that there is not a single romanization method; those languages usually have different ones which are used by different people (Japanese for example has two common romanizations).
So it really depends on the actual language you are working with; while you might be able to make it work for some languages another problem would be to detect which language you are actually working with (e.g. Japanese and Chinese share a lot of characters but meanings, pronounciations and as such romanizations are usually incompatible). Especially for simple santization of file names, I don’t think it is worth to invest such an amount of work and processing time into it.
Maybe you should work in a different direction: Make your file names simply work as unicode filenames. There are actually a very few number of characters that are truly invalid in file systems (*|\/:"<>?) so it would be way easier to simply filter those out and otherwise support unicode file names.
You could run it through your existing sanitizer, then anything not latin, you could convert to punycode
So, as i understand you need some character relation tables for every language, and replace characters by relation in this table.
By example, for translit russian symbols to latin synonyms, we use this tables =) Or classes, which use this tables =)
It's intresting, i finded it right now http://derickrethans.nl/projects.html#translit
Related
When one creates web content in languages different than English the problem of search engine optimized and user friendly URLs emerge.
I'm wondering whether it is the best practice to use de-accented letters in URLs -- risking that some words have completely different meanings with and without certain accents -- or it is better to stick to the usage of non-english characters where appropriate sacrificing the readability of those URLs in less advanced environments (e.g. MSIE, view source).
"Exotic" letters could appear anywhere: in titles of documents, in tags, in user names, etc, so they're not always under the complete supervision of the maintainer of the website.
A possible approach of course would be setting up alternate -- unaccented -- URLs as well which would point to the original destination, but I would like to learn your opinions about using accented URLs as primary document identifiers.
There's no ambiguity here: RFC3986 says no, that is, URIs cannot contain unicode characters, only ASCII.
An entirely different matter is how browsers represent encoded characters when displaying a URI, for example some browsers will display a space in a URL instead of '%20'. This is how IDN works too: punycoded strings are encoded and decoded by browsers on the fly, so if you visit café.com, you're really visiting xn--caf-dma.com. What appears to be unicode chars in URLs is really only 'visual sugar' on the part of the browser: if you use a browser that doesn't support IDN or unicode, the encoded version won't work because the underlying definition of URLs simply doesn't support it, so for it to work consistently, you need to % encode.
When faced with a similar problem, I took advantage of URL rewriting to allow such pages to be accessible by either the accented or unaccented character. The actual URL would be something like
http://www.mysite.com/myresume.html
And a rewriting+character translating function allows this reference
http://www.mysite.com/myresumé.html
to load the same resource. So to answer your question, as the primary resource identifier, I confine myself to 0-9, A-Z, a-z and the occasional hyphen.
Considering URLs with accents often tend to end up looking like this :
http://fr.wikipedia.org/wiki/%C3%89l%C3%A9phant
...which is not that nice... I think we'll still be using de-accented URLs for some time.
Though, things should get better, as accented URLs are now accepted by web browsers, it seems.
The firefox 3.5 I'm currently using displays the URL the nice way, and not with %stuff, btw ; this seems to be "new" since firefox 3.0 (see Firefox 3: UTF-8 support in location bar) ; so, not probably not supported in IE 6, at least -- and there are still quite too many people using this one :-(
Maybe URL with no accent are not looking the best that could be ; but, still, people are used to them, and seem to generally understand them quite well.
You should avoid non-ASCII characters in URLs that may be entered in browser manually by users. It's ok for embedded links pre-encoded by server.
We found out that browser can encode the URL in different ways and it's very hard to figure out what encoding it uses. See my question on this issue,
Handling Character Encoding in URI on Tomcat
There are several areas in a full URL, and each one might has different rules.
The protocol is plain ASCII.
The DNS entry is governed by IDN (International Domain Names) rules, and can contain (most) of the Unicode characters.
The path (after the first /), the user name and the password can again be everything. They are escaped (as %XX), but those are just bytes. What is the encoding of these bytes is difficult to know (is interpreted by the http server).
The parameters part (after the first ?) is passed "as is" (after %XX unescapeing) to some server-side application thing (php, asp, jsp, cgi), and how that interprets the bytes is another story).
It is recommended that the path/user/password/arguments are utf-8, but not mandatory, and not everyone respects that.
So you should definitely allow for non-ASCII (we are not in the 80s anymore), but exactly what you do with that might be tricky. Try to use Unicode and stay away from legacy code pages, tag your content with the proper encoding/charset if you can (using meta in html, language directives for asp/jsp, etc.)
we get book titles from different sources (library systems) (with possibly different encoding, but mostly utf8). These strings are shown in the web and via export to Endnote and RefWorks. RefWorks (windows Quotation system) does not accept any other encoding than ANSI.
In the RIS/Refworks export, activating the line
$smarty = iconv("UTF-8", "Windows-1252", $smarty);
Example string
Diphosphen-komplexes (CO) 5CrPhPPPhCr(CO) 5
does suddenly cut off everything after the first subscript char (the rectangles). These chars are also not correctly printed in HTML but this output is okay because nothing is cut off. In UTF-8 export file encoding nothing is cut off, too. Despite that, the Windows software can't read UTF-8.
The simplest solution would be to convert any subscript number to a regular number. Everything would work quite well then. But I could not find any simple solution to this. Working with hex codes is the only thing I could imagine. This solutions is also preferred for use in our Solr index.
Anybody knows a better solutions?
The example string contains Private Use code points such as U+E5F8. By definition, no standard assigns any meaning to them; their use is purely by private agreements. It is thus impossible to convert them to anything, or to do anything with them, without knowing or inferring the private agreements involved. Some systems use Private Use code points to represent some symbols that are assigned to those points in some special font. Knowing what that font is and inspecting it may thus help to find out the agreement.
The conversion would need to be coded separately, in an ad hoc manner, since there is an an hoc agreement involved.
“ANSI”, which here means windows-1252, does not contain any subscript characters. In the context of a chemical formula, replacing subscript digits by normal digits does not change the meaning, and the formula is understandable, though it looks unprofessional.
When converting to HTML format (or other rich text format), you can use normal digits wrapped in elements that cause subscript rendering (or otherwise style them). HTML has the sub element for this, but its implementations differ between browsers and tend to be a poor quality, so a better approach is to generate <span class=sub>...</span> and use CSS to set the vertical position and font size.
Is there a way to select in mysql words that are only Chinese, only Japanese and only Korean?
In english it can be done by:
SELECT * FROM table WHERE field REGEXP '[a-zA-Z0-9]'
or even a "dirty" solution like:
SELECT * FROM table WHERE field > "0" AND field <"ZZZZZZZZ"
Is there a similar solution for eastern languages / CJK characters?
I understand that Chinese and Japanese share characters so there is a chance that Japanese words using these characters will be mistaken for Chinese words. I guess those words would not be filtered.
The words are stored in a utf-8 string field.
If this cannot be done in mysql, can it be done in PHP?
Thanks! :)
edit 1: The data does not include in which language the string is therefore I cannot filter by another field.
edit 2: using a translator api like bing's (google is closing their translator api) is an interesting idea but i was hoping for a faster regex-style solution.
Searching for a UTF-8 range of characters is not directly supported in MySQL regexp. See the mySQL reference for regexp where it states:
Warning The REGEXP and RLIKE operators
work in byte-wise fashion, so they are
not multi-byte safe and may produce
unexpected results with multi-byte
character sets.
Fortunately in PHP you can build such a regexp e.g. with
/[\x{1234}-\x{5678}]*/u
(note the u at the end of the regexp). You therefore need to find the appropriate ranges for your different languages. Using the unicode code charts will enable you to pick the appropriate script for the language (although not directly the language itself).
You can't do this from the character set alone - especially in modern times where asian texts are frequently "romanized", that is, written with the roman script, that said, if you merely want to select texts that are superficially 'asian', there are ways of doing that depending on just how complicated you want to be and how accurate you need to be.
But honestly, I suggest that you add a new "language" field to your database and ensuring that it's populated correctly.
That said, here are some useful links you may be interested in:
Detect language from string in PHP
http://en.wikipedia.org/wiki/Hidden_Markov_model
The latter is relatively complex to implement, but yields a much better result.
Alternatively, I believe that google has an (online) API that will allow you to detect, AND translate a language.
An interesting paper that should demonstrate the futility of this excercise is:
http://xldb.lasige.di.fc.ul.pt/xldb/publications/ngram-article.pdf
Finally, you ask:
If this cant be done in mysql - how can it be done in PHP?
It will likely to be much easier to do this in PHP because you are more able to perform mathematical analysis on the language string in question, although you'll probably want to feed the results back into the database as a kludgy way of caching the results for performance reasons.
you may consider another data structure that contains the words and or characters, and the language you want to associate them with.
the 'normal' eastern ascii characters will associate to many more languages than just English for instance, just as other characters may associate to more than just Chinese.
Korean mostly uses its own alphabet called Hangul. Occasionally there will be some Han characters thrown in.
Japanese uses three writing systems combined. Of these, Katakana and Hiragana are unique to Japanese and thus are hardly ever used in Korean or Chinese text.
Japanese and Chinese both use Han characters though which means the same Unicode range(s), so there is no simple way to differentiate them based on character ranges alone!
There are some heuristics though.
Mainland China uses simplified characters, many of which are unique and thus are hardly ever used in Japanese or Korean text.
Japan also simplified a small number of common characters, many of which are unique and thus will hardly ever be used in Chinese or Korean text.
But there are certainly plenty of occasions where the same strings of characters are valid as both Japanese and Chinese, especially in the case of very short strings.
One method that will work with all text is to look at groups of characters. This means n-grams and probably Markov models as Arafangion mentions in their answer. But be aware that even this is not foolproof in the case of very short strings!
And of course none of this is going to be implemented in any database software so you will have to do it in your programming language.
First, a brief example, let's say I have this /[0-9]{2}°/ RegEx and this text "24º". The text won't match, obviously ... (?) really, it depends on the font.
Here is my problem, I do not have control on which chars the user uses, so, I need to cover all possibilities in the regex /[0-9]{2}[°º]/, or even better, assure that the text has only the chars I'm expecting °. But I can't just remove the unknown chars otherwise the regex won't work, I need to change it to the chars that looks like it and I'm expecting. I have done this through a little function that maps the "look like" to "what I expect" and change it, the problem is, I have not covered all possibilities, for example, today I found a new -, now we got three of them, just like latex =D - -- --- ,cool , but the regex didn't work.
Does anyone knows how I might solve this?
There is no way to include characters with a "similar appearance" in a regular expression, so basically you can't.
For a specific character, you may have luck with the Unicode specification, which may list some of the most common mistakes, but you have no guarantee. In case of the degree sign, the Unicode code chart lists four similar characters (\u02da, \u030a, \u2070 and \u2218), but not your problematic character, the masculine ordinal indicator.
Unfortunately not in PHP. ASP.NET has unicode character classes that cover things like this, but as you can see here, :So covers too much. Also as it's not PHP doesn't help anyway. :)
In PHP you are going to be limited to selecting the most common character sets and using them.
This should help:
http://unicode.org/charts/charindex.html
There is only one degree symbol. Using something that looks similar is not correct. There are also symbols for degree Fahrenheit and celsius. There are tons of minus signs unfortunately.
Your regular expression will indeed need to list all the characters that you want to accept. If you can't know the string's encoding in advance, you can specify your regular expression to be UTF-8 using the /u modifier in PHP: "/[0-9]{2}[°º]/u" Then you can include all Unicode characters that you want to accept in your character class. You will need to convert the subject string to UTF-8 also before using the regex on it.
I just stumbled into good references for this question:
http://www.unicode.org/Public/6.3.0/ucd/NameAliases.txt
https://docs.python.org/3.4/library/unicodedata.html#unicodedata.normalize
https://www.rfc-editor.org/rfc/rfc3454.html
Ok, if you're looking to pull temp you'll probably need to start with changing a few things first.
temperatures can come in 1 to 3 digits so [0-9]{1,3} (and if someone is actually still alive to put in a four digit temperature then we are all doomed!) may be more accurate for you.
Now the degree signs are the tricky part as you've found out. If you can't control the user (more's the pity), can you just pull whatever comes next?
[0-9]{1,3}.
You might have to beef up the first part though with a little position handling like beginning of the string or end.
You may also exclude all the regular characters you don't want.
[0-9]{1,3}[^a-zA-Z]
That will pick up all the punctuation marks (only one though).
I got a question regarding regexp in general. I'm currently building a register form where you can enter the full name (given name and family name) however I cant use [a-zA-Z] as a validation check because that would exclude everyone with a "foreign" character.
What is the best way to make sure that they don't enter a symbol, in both php and javascript?
Thanks in advance!
The correct solution to this problem (in general) is POSIX character classes. In particular, you should be able to use [:alpha:] (or [:alphanum:]) to do this.
Though why do you want to prevent users from entering their name exactly as they type it? Are you sure you're in a position to tell them exactly what characters are allowed to be in their names?
You first need to conceptually distinguish between a "foreign" character and a "symbol." You may need to clarify here.
Accounting for other languages means accounting for other code pages and that is really beyond the scope of a simple regexp. It can be done, but on a higher level, the codepages have to work.
If you strictly wanted your regexp to fail on punctuation and symbols, you could use [^[:punct:]], but I'm not sure how the [:punct:] POSIX class reacts to some of the weird unicode symbols. This would of course stop some one from putting in "John Smythe-Jones" as their name though (as '-' is a punctuation character), so I would probably advise against using it.
I don’t think that’s a good idea. See How to check real names and surnames - PHP
I don't know how you would account for what is valid or not, and depending on your global reach, you will probably not be able to remove anything without locking out somebody. But a Google search turned this up which may be helpful.
http://nadeausoftware.com/articles/2007/09/php_tip_how_strip_symbol_characters_web_page
You could loop through the input string and use the String.charCodeAt() function to get the integer character code for each character. Set yourself up with a range of acceptable characters and do your comparison.
As noted POSIX character classes are likely the best bet. But the details of their support (and alternatives) vary very much with the details of the specific regex variant.
PHP apparently does support them, but JavaScript does not.
This means for JavaScript you will need to use character ranges: /[\u0400-\u04FF]/ matches any one Cyrillic character. Clearly this will take some writing, but not the XML 1.0 Recommendation (from W3C) includes a listing of a lot of ranges, albeit a few years old now.
One approach might be to have a limited check on the client in JavaScript, and the full check only server side.