I am using iconv to convert string from CP1251 to UTF-8
Problem is that string length before conversion is 4 bytes, after 8.
After converting i send message to Apple servers, where is length is limited.
How I can get conversion and keep the same length?
There is no way you can do it. In UTF-8 one-byte codes are used only for the ASCII values 0 through 127. In this case the UTF-8 code has the same value as the ASCII code. The high-order bit of these codes is always 0.
As you are trying to encode non-ASCII characters, you'll get more, then 1 byte per character.
The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets
http://en.wikipedia.org/wiki/UTF-8#Overlong_encodings
Related
Assuming UTF-8 encoding, and strlen() in PHP, is it possible that this string has a length of 4?
I'm only interested to know about strlen(), not other functions
This is the string:
$1�2
I have tested it on my own computer, and I have verified UTF-8 encoding, and the answer I get is 6.
I don't see anything in the manual for strlen or anything I've read on UTF-8 that would explain why some of the characters above would count for less than one.
PS: This question and answer (4) comes from a mock test for ZCE I bought on Ebay.
how about using mb_strlen() ?
http://lt.php.net/manual/en/function.mb-strlen.php
But if you need to use strlen, its possible to configure your webserver by setting mbstring.func_overload directive to 2, so it will automatically replace using of strlen to mb_strlen in your scripts.
The string you posted is six character long: $1�2 (dollar sign, digit one, lowercase i with diaeresis, upside-down question mark, one half fraction, digit two)
If strlen() was called with a UTF-8 representation of that string, you would get a result of nine (probably, though there are multiple representations with different lengths).
However, if we were to store that string as ISO 8859-1 or CP1252 we would have a six byte long sequence that would be legal as UTF-8. Reinterpreting those 6 bytes as UTF-8 would then result in 4 characters: $1�2 (dollar sign, digit one, Unicode Replacement Character, digit 2). That is, the UTF-8 encoding of the single character '�' is identical to the ISO-8859-1 encoding of the three characters "�".
The replacement character often gets inserted when a UTF-8 decoder reads data that's not valid UTF-8 data.
It appears that the original string was processed through multiple layers of misinterpretation; by the use of a UTF-8 decoder on non-UTF-8 data (producing $1�2), and then by whatever you used to analyze that data (producing $1�2).
need to use Multibyte String Function mb_strlen() like:
mb_strlen($string, 'UTF-8');
It's likely that at some point between the preparation of the question and your reading of it some process has mangled non-ASCII characters in it, so the question was originally about some string with 4 characters in it.
The sequence � is obtained when you encode the replacement character U+FFFD (�) in UTF-8 and interpret the result in latin1. This character is used as a replacement for byte sequences that don't encode any character when reading text from a file, for example. What has happened is likely this:
The original question, stored in a latin1 text file, had: $1¢2 (you can replace ¢ with any non-ASCII character)
The file was read by a program that used UTF-8. Since the byte corresponding to ¢ could not be interpreted, the program substituted it and read the text $1�2. This text was then written out using UTF-8, resulting in $1\xEF\xBF\xBD2 in the file.
Then some third program comes that reads the file in latin1, and shows $1�2.
No.
I'll use a proof by contradiction.
strlen counts bytes, so with a strlen of 4, there would need to be exactly 4 bytes in that string.
UTF8 encoding needs at least 1 byte per character.
We have established that:
there are 4 bytes
a character is represented by no less than 1 byte
...yet, we have 6 characters....which is a contradiction. So, no.
However, what's not totally clear is which character set the displaying software(eg, the web browser) is using to intepret the string. It could use some uncommon encoding scheme where a character can be represented by less than 8 bits. If this were the case, then 4 bytes could display as 6 characters. So, the string could be utf8, but the browser could decide to interpret it as, say, some 5 bit character set.
Many UTF-8 characters take several bytes instead of one. That's how UTF-8 is constructed (That's how you can have so many characters in a single set).
Try mb_strlen() instead.
This question already has answers here:
strlen() and UTF-8 encoding
(6 answers)
Closed 4 years ago.
I have a string with this content :
$myString = 'Câmara de Dirigentes Lojistas';
This string have 29 chars. BUT when i call strlen, it returns 30 ! Even when i call var_dump($myString), that's the result :
114:string 'Câmara de Dirigentes Lojistas' (length=30)
What is going on here ? Maybe the problem is related to the special char â ?
That's the right behavior since you are using UTF-8 encoding.
Please see this note on strlen() documentation
Note:
strlen() returns the number of bytes rather than the number of characters in a string.
As your string have multi-byte characters (â), PHP uses two bytes to represent it.
To have the right string length, you must use the mb_strlen() function:
mb_strlen("â"); // 1
strlen("â"); // 2
There are several definitions of the "length" of a string, because there are a variety of tricks used to represent the huge range of accented characters, variants, and non-alphabetic scripts used around the world.
The number of bytes the string takes up. This is the easiest to calculate, but not always what is expected. For instance, in UTF-16, every code point takes up either 2 or 4 bytes; in UTF-8, code points take up 1, 2, 3, or 4 bytes. This is what strlen and most PHP functions work with.
The number of "code points": separate symbols in the character set. This is the next easiest, and the next most common, but is generally a compromise between bytes and "graphemes" (see below) - there aren't many cases where it's particularly useful to count é as 2 "characters" just because it's represented with a combining diacritic. In PHP you can use mb_strlen to count these, telling it your string's character encoding.
The number of "graphemes": separate symbols a reader would recognise. This is the most intuitive meaning, but the hardest for a computer to define. In PHP you can use grapheme_strlen, as long as you have ensured your string is encoded as UTF-8.
There is an issue with the character â as it is a special character which uses a different encoding. Characters like this are actually double characters this is why its giving 30 and not 29
To fix this, you need to use mb_strlen() with encoding
$myString = 'Câmara de Dirigentes Lojistas';
echo mb_strlen($myString,'utf8')
NOTE : If mb_strlen is undefined, then you will have to enable mb extension in your php settings
Interestingly the â char exists in extended ascii, i.e. it can be represented by just one byte, you can try it with this code:
$str = utf8_decode('Câmara de Dirigentes Lojistas');
echo 'length is ' . strlen($str);
that will output length is 29.
So as you see the thing is that when a char is not plain ascii (127 char ascii table) then PHP assumes UTF-8 automatically.
I am trying to decode this special character: "ß", if I use "ord()", I get "C3"
echo "ord hex--> " . dechex(ord('ß'));
...but that doesn't look good; so i tried "bin2hex()", now I get "C39F" (what?).
echo "bin2hex --> " . bin2hex('ß');
By using an Extended ASCII Table from the Internet, i know that the correct hexadecimal value is "DF", so i now tried "hex2bin()", but that give me some unknown character like this: "�".
echo "hex2bin --> " . hex2bin('DF');
Is it possible to get the "DF" output?
You're on the right path with bin2hex, what you're confused about is merely the encoding. Currently you're seeing the hex value of ß for the UTF-8 encoding, because your string is encoded in UTF-8. What you want is the hex value for that string in some other encoding. Let's assume "Extended ASCII" refers to ISO-8859-1, as it colloquially often does (but doesn't have to):
echo bin2hex(iconv('UTF-8', 'ISO-8859-1', 'ß'));
Now, having said that, I have no idea what you'd use that information for. There are many valid "hex values" for the character ß in various different encodings; "Extended ASCII" is just one possible answer, and it's a vague answer to be sure, since "Extended ASCII" has very little practical meaning with hundreds of different "Extended ASCII" charsets available.
ASCII goes from 0x00 to 0x7F. This is not enough to represent all the characters needed so historically old Windows OSes used the available space in a byte (from 0x80 to 0xFF) to represent different characters depending on the localization. This is what codepages are: an arbitrary mapping of non-ASCII values to non-ASCII characters. What you call "extended ASCII" is IMO an inappropriate name for a codepage.
The assumption 1 byte - 1 character is dead and (if not) must die.
So actually what you are seeing is the UTF-8 representation of ß. If you want to see the UNICODE code point value of ß (or any other character) just show its UTF-32 representation that AFAIK is mapped 1:1.
// Print 000000df
echo bin2hex(iconv('UTF-8', 'UTF-32BE', 'ß')));
bin2hex() should be fine, as long as you know what encoding you are using.
The C3 output you get appears to be the first byte of the two-byte representation of the character in UTF-8 (what incidentally means that you've configured your editor to save files in such encoding, which is a good idea in 2017).
The ord() function does not accept arbitrary encodings, let alone Unicode-compatible ones such as UTF-8:
Returns the ASCII value of the first character of string.
ASCII (a fairly small 7-bit charset) does not have any encoding for the ß character (aka U+00DF LATIN SMALL LETTER SHARP S). Seriously. ASCII does not even have a DF position (it goes up to 7E).
I have a web application, written in PHP, based on UTF-8 (both PHP and MySQL are on UTF-8). Everything is beautiful - no problem with special characters.
However, I had to build an export to XML with encoding ISO-8859-2 (Polish), so I picked DomDocument because it has built in encoding conversion.
But when I had sent the XML to my partner for validation, he said that one of tags have too many characters. It was strange because it had the specific maximum number of characters. Then I have opened the file in HexEditor and saw that every special character has two bytes.
I have tried to convert the result with iconv and mb_convert_encoding.
Iconv says:
iconv() [<a href='function.iconv'>function.iconv</a>]: Detected an illegal character in input string in file application/controllers/report/export.php at 169
mb_convert_encoding is simply deleting all special characters and result is encoded in ASCII.
Is there a way to convert the output of DomDocument to one-byte characters?
Thanks in advance!
One problem when switching between encodings is that, even with transliteration, not all characters are representable in other encodings in a single byte.
For example, consider the EURO SIGN, a character that takes 3 bytes when encoded in UTF-8. If you look at the charset support page, you can see that ISO-8859-2 is not listed.
Since there is not a single character to represent the euro sign, then transliteration does its best to still represent it in the output
echo iconv( 'UTF-8', 'ISO-8859-2//TRANSLIT', '€' ); // EUR
In this example, we still end up with 3 bytes to represent the euro sign after transliterating.
EDIT
P.S. The NOTICE level error you're getting is because you executed iconv() without the transliteration flag. And as I highlighted above, the EURO SIGN doesn't exist in ISO-8859-2, so you clearly have at least one character in your data that also doesn't exist in ISO-8859-2, so you'll have to use transliteration. Just know that it doesn't guarantee that you'll get down to 1 byte/char.
PHP's str_replace() was intended only for ANSI strings and as such can mangle UTF-8 strings. However, given that it's binary-safe would it work properly if it was only given valid UTF-8 strings as arguments?
Edit: I'm not looking for a replacement function, I would just like to know if this hypothesis is correct.
Yes. UTF-8 is deliberately designed to allow this and other similar non-Unicode-aware processing.
In UTF-8, any non-ASCII byte sequence representing a valid character always begins with a byte in the range \xC0-\xFF. This byte may not appear anywhere else in the sequence, so you can't make a valid UTF-8 sequence that matches part of a character.
This is not the case for older multibyte encodings, where different parts of a byte sequence are indistinguishable. This caused a lot of problems, for example trying to replace an ASCII backslash in a Shift-JIS string (where byte \x5C might be the second byte of a character sequence representing something else).
It's correct because UTF-8 multibyte characters are exclusively non-ASCII (128+ byte value) characters beginning with a byte that defines how many bytes follow, so you can't accidentally end up matching a part of one UTF-8 multibyte character with another.
To visualise (abstractly):
a for an ASCII character
2x for a 2-byte character
3xx for a 3-byte character
4xxx for a 4-byte character
If you're matching, say, a2x3xx (a bytes in ASCII range), since a < x, and 2x cannot be a subset of 3xx or 4xxx, et cetera, you can be safe that your UTF-8 will match correctly, given the prerequisite that all strings are definitely valid UTF-8.
Edit: See bobince's answer for a less abstract explanation.
Well, I do have a counter example: I have a UTF8 encoded settings ".ini' file specifying appliation settings like email sender name. it says something like:
email_from = Märta
and I read it from there to variable $sender. Now that I replace the message body (UTF8 again)
regards
{sender}
$message = str_replace("{sender}",$sender_name,$message);
The email is absolutely correct in every respect but the sender is totally broken. There are other cases (like explode() ) when something goes wrong with a UTF string. It is healthy before the conversion but not after it. Sorry to say there seems to be no way of correcting this behaviour.
Edit: Actually, explode() is involved in parsing the .ini file so the problem may well lie in that very function so the str_replace() may well be innocent.
No you cannot.
From practice I am telling you if you have some multibyte symbols like ◊ etc, and others are non-multibyte it wont work correctly, because there are symbols that take 2-4 to place them,
str_replace takes fixed bytes, and replaces... In result we have something that isn't any symbols trash etc.
Yes, I think this is correct, at least I couldn't find any counter-example.