Library for detecting unicode strings with single byte encoded UTF8 characters in them

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Language: PHP

1.1.0 2013-01-02 22:00 UTC


MendedString is a PHP class for detecting unicode strings with single byte encoded UTF-8 characters in them, for example like those created by using PHP's utf8_encode() function on a string with non-ASCII characters in it and then saving to a data source that supports full UTF-8 encoding, like MongoDB.

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Use case

We created MendedString due to our reliance in legacy code on the PHP utf8_encode and utf8_decode builtin functions. Whenever we saved user data to our datastore (in this case MongoDB) we would have to utf8_encode() it first and remember to utf8_decode() it on output back to the user.

With correct encodings in PHP and the browser set this shouldn't be required, what with strings in MongoDB being stored in the BSON document format which uses UTF-8, this shouldn't be necessary. While migrating our code to use the correct encodings we found that we lots of data already stored in Mongo using single-byte armouring of multi-byte characters (via utf8_encode) and to be able to ditch all such armouring we'd need to first migrate the existing data.

MendedString does this by checking for these characters and decoding them appropriately, multiple times if needed, until you have a native PHP string encoded with unicode.

Note: it doesn't use mb_detect_encoding or it's ilk from the multibyte extension as we found this unreliable for detecting single-byte armoured characters, only actual multibyte characters which was useless for our purposes.


If you're using Composer for your project you can just add serverdensity/mendedstring to your requirements.

Otherwise you'll need to include/require mendedstring/src/ServerDensity/MendedString.php in your code.


To fix a broken (or possibly broken) string with unicode characters in just pass the string into a new \ServerDensity\MendedString\MendedString instance. Each instance is immutable, so to fix a new string you need to create a new instance, e.g.:

use \ServerDensity\MendedString\MendedString;
// The MendedString class exists in the MendedString module to make autoloading
// a bit more efficient.

$broken = utf8_encode('hello world' . utf8_encode('«ταБЬℓσ»'));
$mended = new MendedString($broken);

// Mended strings are lazy-converted, you either have to call ->getConverted()
// or use it as a string (e.g. cast it, concat it with another string etc.) like so:
echo (string)$mended;


MendedString is BSD licensed, feel free to use and abuse, but keep the LICENSE file intact.