Writing Javascript UTF Regular Expression in PHP

Question

I need to rewrite this javascript regular expression in PHP for use with preg_replace:

var PATTERN = /([\ud800-\udbff])([\udc00-\udfff])/g;

If I use:

$strText = preg_replace("/([\ud800-\udbff])([\udc00-\udfff])/", "emoji", $strText);

I get:

Compilation failed: PCRE does not support \L, \l, \N{name}, \U, or \u at offset 3

If I use: preg_replace("/([\x{d800}-\x{dbff}])([\x{dc00}-\x{dfff}])/", "emoji", $strText); I get Compilation failed: character value in \x{...} sequence is too large at offset 9. — OneCleverMonkey
– OneCleverMonkey, Commented Oct 15, 2014 at 18:36
As an aside, the capture groups are useless and the first range can be replaced with \p{Cs}: ~(*UTF8)\p{Cs}[\x{dc00}-\x{dfff}]~ — Casimir et Hippolyte
– Casimir et Hippolyte, Commented Oct 15, 2014 at 19:16

Smern · Accepted Answer · 2014-10-15 19:16:47Z

1

Try the following:

preg_replace("/([\x{d800}-\x{dbff}])([\x{dc00}-\x{dfff}])/u", "emoji", $strText);

PCRE doesn't support the \uXXXX format, so you can use \x{XXXX} instead. Also you'll need the u modifier (at end of regex) for dealing with UTF-8

Information on syntax from http://www.regular-expressions.info/unicode.html

Perl and PCRE do not support the \uFFFF syntax. They use \x{FFFF} instead.

Information on u modifier 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. This modifier is available from PHP 4.1.0 or greater on Unix and from PHP 4.2.3 on win32. UTF-8 validity of the pattern and the subject is checked since PHP 4.3.5. 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.

edited Oct 15, 2014 at 19:16

answered Oct 15, 2014 at 18:56

Smern

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3 Comments

OneCleverMonkey Over a year ago

I get Compilation failed: disallowed Unicode code point (>= 0xd800 && <= 0xdfff) at offset 9 with this.

Smern Over a year ago

@OneCleverMonkey, I searched that error and found this... stackoverflow.com/questions/21666895/…, it seems weird, but can you try replacing the leading D's with E's?

Smern Over a year ago

Or convert to UTF8 (presumably from UTF16) before doing your regex, wisercoder.com/php-preg_match-failing-reason-blame-utf-16

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