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I recently noticed that some of my blog posts, most notably my Templates in YARPP 3 article, was producing a PHP error:

Warning: preg_match() [function.preg-match]: Compilation failed: unrecognized character after (?< at offset 3 in /…/html/blog/wp-content/plugins/wp-syntax/geshi/geshi.php on line 2132

This seemed to be coming from the version 1.0.8.4 version of Geshi I had installed. A quick google search for “geshi line 2132” gives you over a thousand errors, so this seems to be common issue. Geshi is a fabulous and popular syntax highlighter and is the core component of the WP-Syntax plugin for WordPress.

I did some digging around and realized that the issue was with the compilation of this monstrosity of a regular expression, used (as far as I can tell) to identify PHP code snippets, for example the <?php … ?> keywords:

/(?<start><\\?(?>php\b)?)(?:
(?>[^\"'?\\/<]+)|
\\?(?!>)|
(?>'(?>[^'\\\\]|\\\\'|\\\\\\\|\\\\)*')|
(?>\"(?>[^\"\\\\]|\\\\\"|\\\\\\\\|\\\\)*\")|
(?>\\/\\*(?>[^\\*]|(?!\\*\\/)\\*)*\\*\\/)|
\\/\\/(?>.*?$)|
\\/(?=[^*\\/])|
<(?!<<)|
<<<(?<phpdoc>\w+)\s.*?\s\k<phpdoc>
)*(?<end>\\?>|\Z)/sm

Not knowing exactly where to start in diagnosing this crazy expression, I simply disabled those “script delimiters” in the geshi/php.php file. The sections I commented out are lines 1080-1101. Now the script delimiters like <?php don’t get highlighted nicely, but I feel that’s a small price to pay for eliminating these errors. Another solution for the WP-Syntax users seems to be to downgrade to 0.9.4. Hopefully in the near future an update to Geshi will come out which fixes this issue once and for all.

Related posts:

1. Yet Another Related Posts Plugin
2. Modifiying WordPress plugin activation behavior
3. Keep up with Yet Another Related Posts Plugin with RSS!
4. Yet Another Related Posts Plugin 2.0
5. Using Templates with YARPP 3

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Tags: bug, code, error, geshi, PHP, regular expression, WordPress, WordPress Planet, YARPP

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This entry was posted on Saturday, June 13th, 2009 at 3:15 pm and is filed under how to. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.