Source Code Syntax Highlighting in PHP

Fri 03 January 2003

Source Code Syntax Highlighting in PHP

They said programming is an art, and syntax highlighting of source code really makes them look artistic.

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Updated: This has been superseded by the newer version that also can acts as a WordPress plugin.

Scott Yang