转载自http://www.21andy.com/blog/20060915/427

[code]<?php
function format_output($output) {
/****************************************************************************
* Takes a raw string ($output) and formats it for output using a special
* stripped down markup that is similar to HTML
****************************************************************************/

$output = htmlspecialchars(stripslashes($output));
$output = ereg_replace(' ', '&nbsp;&nbsp;', $output);
/* new paragraph */
$output = str_replace('[p]', '<p>', $output);

/* bold */
$output = str_replace('[b]', '<b>', $output);
$output = str_replace('[/b]', '</b>', $output);

/* italics */
$output = str_replace('[i]', '<i>', $output);
$output = str_replace('[/i]', '</i>', $output);

/* preformatted */
$output = str_replace('[pre]', '<pre>', $output);
$output = str_replace('[/pre]', '</pre>', $output);

$output = str_replace('[u]', '<u>', $output);
$output = str_replace('[/u]', '</u>', $output);

/* indented blocks (blockquote) */
$output = str_replace('[indent]', '<blockquote>', $output);
$output = str_replace('[/indent]', '</blockquote>', $output);

/* anchors */
$output = ereg_replace('[anchor=&quot;([[:graph:]]+)&quot;]', '<a name="1"></a>', $output);

/* links, note we try to prevent javascript in links */
$output = str_replace('[link=&quot;javascript', '[link=&quot; javascript', $output);
$output = ereg_replace('[link=&quot;([[:graph:]]+)&quot;]', '<a href="1">', $output);
$output = str_replace('[/link]', '</a>', $output);

$output = ereg_replace('[img=&quot;([[:graph:]]+)&quot;]', '<div align="center"><img src="1">', $output);
$output = str_replace('[/img]', '</img></div>', $output);



return nl2br($output);
}
?>[/code]