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I've got the string

$result = "bei einer Temperatur, die etwa 20 bis 60°C unterhalb des Schmelzpunktes der kristallinen Modifikation"

which comes straight from a MySQL table. The table, and the php headers are both set to UTF-8

I want to strip the 'degree' symbol: http://en.wikipedia.org/wiki/Degree_symbol and replace it with the word 'degrees' to get:

"bei einer Temperatur, die etwa 20 bis 60degreesC unterhalb des Schmelzpunktes der kristallinen Modifikation"

but I can't get it to work with preg_replace.

If I do: 

$result = preg_replace('/\xB0/u'," degrees ", $result ); - I get an empty string

And if I do::

$result = preg_replace('/\u00B0/u'," degrees ", $result ); - I get the error:

Warning: preg_replace() [function.preg-replace]: Compilation failed: PCRE does not support \L, \l, \N, \U, or \u at offset 1 in /var/www/html/includes/classes/redeyeTable.inc.php on line 75

I'm not great with encodings... what am I doing wrong here?

Ed Lewis
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  • The first solution you post works perfectly for me. – Sjoerd Jun 29 '10 at 12:52
  • According to this page (and to your error message BTW), you cannot use \u http://fr.php.net/manual/en/reference.pcre.pattern.differences.php – greg0ire Jun 29 '10 at 12:53
  • Are you sure you have the same symbol? Unicode has many similar characters. – Kobi Jun 29 '10 at 12:54
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    The first one should work fine. But if you are just replacing that, you can use the faster str_replace() instead. – quantumSoup Jun 29 '10 at 12:57
  • Thanks for the comments - I agree the first option should work. I have no idea why it strips ALL text out. I'm finding PHP and UTF-8 to be a rather tricky combination. I'm just using a standard ubuntu 10.04 install and the latest stable PHP build, don't know why character handling fails at every turn. – Ed Lewis Jun 29 '10 at 13:36

2 Answers2

30

Use

$result = preg_replace('/\x{00B0}/u'," degrees ", $result );

Please see here for more information on the \x{FFFF}-syntax.

It's important to note the difference between \xB0 and \x{00B0}:

  • \xB0 denotes a single character with hex-code B0 (176 decimal) which is the degree symbol (°) in ISO-8859-1 for example
  • \x{00B0} denotes the unicode codepoint U+00B0 which describes the degree symbol (°) in the unicode system. This codepoint will be encoded using two bytes \xC2\xB0 when using UTF-8 encoding.
Community
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Stefan Gehrig
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  • That works! Thank you Stefan and everyone who contributed. My mistake was not using the { } around the unicode codepoint. I appreciate the difference between \xB0 and \x{00B0} - it was more desperate trial and error that had me settling for \xB0 replacement on a unicode string. Stackoverflow once again is a life saver! – Ed Lewis Jun 30 '10 at 13:00
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    @Ed: You could mark the answer as "accepted" to show other users that this is the solution to your problem. – Stefan Gehrig Jul 02 '10 at 06:48
  • I don't know how many hours I spent searching for why my regex to replace some UTF8 chars was not working, and thanks to this trick with \xNN vs \x{NN}, I finally got it right. Many thanks Stefan :-) – dregad Nov 15 '12 at 18:23
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If you use the 'u' modifier, the pattern is supposed to be treated as utf-8, so why not simply write '°' instead of '\u00B0' or '\xB0'?

greg0ire
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    $result = preg_replace('/°/u'," degrees ", $result ); does work.... why doesn't it work giving the string in hex? – Ed Lewis Jun 29 '10 at 13:40