phpregexunicode

PHP - regex to allow Unicode characters

I was using the following regex with preg_replace to filter inputs:

/[^A-Za-z0-9[:space:][:blank:]_<>=@#£€$!?:;%,.\\'\\\"()&+\\/-]/

However this does not allow accented characters like umlauts so I changed it to:

/[^\w[:space:][:blank:]_<>=@#$£€!?:;%,.\\'\\\"()&+\\/-]/u

This however does work with the £ or € characters, nothing is returned, but I need to accept these characters, I have tried escaping them but that doesn't work.

Also I want to create an regex that is similar to just A-Za-z but will allow accented characters, how can I do that?

Solution

  • From http://php.net/manual/en/reference.pcre.pattern.modifiers.php

    u (PCRE_UTF8) This modifier turns on additional functionality of PCRE that is incompatible with Perl. Pattern and subject strings are treated as UTF-8. An invalid subject will cause the preg_* function to match nothing; an invalid pattern will trigger an error of level E_WARNING. Five and six octet UTF-8 sequences are regarded as invalid since PHP 5.3.4 (resp. PCRE 7.3 2007-08-28); formerly those have been regarded as valid UTF-8.

    That means that first you have to make sure the input string is proper UTF-8 text.

    Secondly, have you heard of unicode categories? If not, head to http://www.regular-expressions.info/unicode.html and search for Unicode categories. For example you could use \p{S} to match all currency symbols, or \p{L} for all letters. Your regex could (probably) be written as follows: /[^\p{L}\p{P}\p{N}\p{S}\p{M}]/.

    This will though match pretty much nothing, as it allows pretty much all characters to be used - ^ at the start of a regex character class (something between [ and ]) means "everything that is not what is in this class will be matched".

    On top of that, your regex will only match input that has a length of exactly one - if you want to match everything, you should begin adding a + after your closing ] to keep matching characters until the pattern fails.

    So, for that sake, what exactly are you trying to achieve? Maybe we can suggest you some more regex improvements if we know what you're trying to do.