How to remove %EF%BB%BF in a PHP string

Question

I am trying to use the Microsoft Bing API.

$data = file_get_contents("http://api.microsofttranslator.com/V2/Ajax.svc/Speak?appId=APPID&text={$text}&language=ja&format=audio/wav");
$data = stripslashes(trim($data));

The data returned has a ' ' character in the first character of the returned string. It is not a space, because I trimed it before returning the data.

The ' ' character turned out to be %EF%BB%BF.

I wonder why this happened, maybe a bug from Microsoft?

How can I remove this %EF%BB%BF in PHP?

Solution 1

You could use substr to only get the rest without the UTF-8 BOM:

// if it’s binary UTF-8
$data = substr($data, 3);
// if it’s percent-encoded UTF-8
$data = substr($data, 9);

Solution 2

You should not simply discard the BOM unless you're 100% sure that the stream will: (a) always be UTF-8, and (b) always have a UTF-8 BOM.

The reasons:

1. In UTF-8, a BOM is optional - so if the service quits sending it at some future point you'll be throwing away the first three characters of your response instead.
2. The whole purpose of the BOM is to identify unambiguously the type of UTF stream being interpreted UTF-8? -16? or -32?, and also to indicate the 'endian-ness' (byte order) of the encoded information. If you just throw it away you're assuming that you're always getting UTF-8; this may not be a very good assumption.
3. Not all BOMs are 3-bytes long, only the UTF-8 one is three bytes. UTF-16 is two bytes, and UTF-32 is four bytes. So if the service switches to a wider UTF encoding in the future, your code will break.

I think a more appropriate way to handle this would be something like:

/* Detect the encoding, then convert from detected encoding to ASCII */
$enc = mb_detect_encoding($data);
$data = mb_convert_encoding($data, "ASCII", $enc);

Solution 3

$data = file_get_contents("http://api.microsofttranslator.com/V2/Ajax.svc/Speak?appId=APPID&text={$text}&language=ja&format=audio/wav");
$data = stripslashes(trim($data));

if (substr($data, 0, 3) == "\xef\xbb\xbf") {
$data = substr($data, 3);
}

Solution 4

It's a byte order mark (BOM), indicating the response is encoded as UTF-8. You can safely remove it, but you should parse the remainder as UTF-8.

View more solutions

Comments

[Lee]

Note: generally speaking, throwing away the BOM is not a good idea. The BOM is there to tell you how the rest of the string should be handled. If you just ignore it, assuming that it's a UTF-8 3-byte BOM, you're setting yourself up for some real problems if/when the encoding ever changes. ... Please have a look at my answer below for more details.

[crdx]

To future googlers: use this solution instead. Throwing away the BOM is a bad idea.

[mpen]

This doesn't appear to work in practice. mb_convert_encoding("\357\273\277some text", 'ASCII', mb_detect_encoding("\357\273\277some text")) yields string(10) "?some text". Notice that it left a question mark in the output.

[Lee]

@mark Unfortunately, that does appear to be true. I had better luck using iconv('UTF-8', 'ASCII//TRANSLIT//IGNORE',"\357\273\277some text") to do the converstion. I guess mb_detect_encoding would be used to detect the initial charset, which would then be passed as the first arg to iconv. This is more of a hack than it should be.

[naw103]

@mark I had to add the following line to get rid of the ? : ini_set('mbstring.substitute_character', "none");

[Gkiokan]

This solution is great! It helped me a lot when I couldn't find the answer. The best logical part is to make a condition, if the BOM Hex Charakters exists, and then delete them. This code seems future save, even when the Server will not send BOM, this function will still works. +1