• Detect whether we are running under WP 1.5+ to pick the unmangling routine. WP1.5 double quote fix suggested by Oliver.
• Eliminate the “Generated by GNU Enscript” text (suggested by Alex), which was caused by a regular expression bug.

Also I found with WP 1.5, you no longer needs to escape backslashes ‘\’ to \.

• Download syntax_hilight-1.3.php

• Download syntax_hilight-1.2.php

A plugin needs to be written, that

• Fixes up the mess wptexturize has left after paragraphing the contents inside <pre /> tag.
• Optionally add syntax highlighting using GNU Enscript, a method that I have previously discussed.
• Can be used as a module outside WordPress to provide syntax highlighting to source files or code pieces.

Result is an updated version syntax highlighter PHP module.

• Download the latest version: syntax_hilight.php (1.3 updated on 9 March 2005)

Usage

To use it with WordPress 1.2/1.5.

• Save the PHP source file into wp-content/plugins/ directory.
• Go to “Plugin Management” page under your WordPress admin interface.
• Activate plugin “Syntax Highlighter Enscript”.

Inside your HTML code, all your <pre /> tag should now be properly formatted. If you wish to add syntax highlighting to a piece of code, you will need to add lang="..." attribute to your <pre /> tag. For example,

<pre lang="python">
if __name__ == '__main__':
    print "Hello Word"
</pre>

The final HTML rendering would be:

if __name__ == '__main__':
    print "Hello Word"

“lang” attribute would need to be supported by GNU Enscript backend. Please check what languages Enscript can support.

To use it outside the context of WordPress, directly as a PHP module, you can call:

$code = 'int main(void) { printf("Hello World\n"); }';
SyntaxHilighter::hilight($code, "c");

To highlight a file on the file system:

SyntaxHilighter::hilght_file('foobar.pl', 'perl');

There are still some unresolved problems:

• Not everyone can run enscript, especially if you are jailed inside PHP safe mode. Well, too bad. Find another host :)
• Line numbering – it should be my next todo item.
• Backslashes are stripped after Save, which makes code listing a challenge. Besides escaping characters like ‘<’, ‘>’ and ‘&’, I also need to escape backslashes to ‘&#92;’. Looks like a WordPress bug to me.

I have some little scripts that I would to publish on the net, and I would like to add some colour before posting in my blog. PHP has this function show_source() that can syntax highlight a file, however it only works on PHP files. Instead of writing parsers and generators for all the programming languages known to mankind out there, I opt for something already been written – GNU Enscript.

I know that Enscript is mainly use to generate Postscript files, but in a tool which I’ve used before, ViewCVS, I saw how it calls Enscript to generate syntax highlighted source code listing. It then took me a few minutes to hack up a wrapper for it in PHP…

• Download the source file: syntax_hilight.php

This is an demonstration of how to use it.

echo syntax_hilight('syntax_hilight.php');

Source Code

/**
 * Syntax hilighting a program source file. It calls enscript(1) to parse and
 * insert HTML tags to produce syntax hilighted version of the source. Since
 * the version of enscript I have does not support PHP hilighting, I will use
 * PHP's show_source() if the source file ends with .php.
 *
 * @param  $filename The filename of the source file to be transformed.
 * @return A text string containing syntax hilighting version of the source,
 *         in HTML.
 */
function syntax_hilight($filename) {
    if ((substr($filename, -4) == '.php')) {
        ob_start();
        show_source($filename);
        $buffer = ob_get_contents();
        ob_end_clean();
    } else {
        $argv = '-q -p - -E --language=html --color '.escapeshellcmd($filename);
        $buffer = array();

        exec("enscript $argv", $buffer);

        $buffer = join("\n", $buffer);
        $buffer = eregi_replace('^.*<PRE>',  '<pre>',  $buffer);
        $buffer = eregi_replace('</PRE>.*$', '</pre>', $buffer);
    }

    // Making it XHTML compatible.
    $buffer = eregi_replace('<FONT COLOR="', '<span style="color:', $buffer);
    $buffer = eregi_replace('</FONT>', '</style>', $buffer);

    return $buffer;
}

Updated: This has been superseded by the newer version that also can acts as a WordPress plugin.