Sometimes, when using Drupal, I find that I want to link to some of my older posts. However, I often have a couple of development checkouts of my site. Consider the case where I have the live site, which can be reached at http://iheartryan.com/, and I have a development checkout, http://localhost/iheartryan/. Now, say I'm trying to link to my Rhythmbox Playlist Folders post. How should I make this link? I have a couple choices:

1. http://iheartryan.com/post/rhythmbox-playlist-folders
2. /post/rhythmbox-playlist-folders

Neither of these will totally work for my purposes. For example, let's say I choose to make a full, absolute path, like #1 above, then when I look at this page in my development checkout, the link will point to the post on the live server. I can't navigate around internally on my dev checkout.

Choice #2 might help with that problem. It is a link to the post on whatever server I happen to be looking at. The problem is that my dev checkout has a different path. So choice #2 will give us a link to: http://localhost/post/rhythmbox-playlist-folders. What we need is a link to http://localhost/iheartryan/post/rhythmbox-playlist-folders.

I have a solution that will cover most of the cases. If you implement this solution on your site, then you can just make a link to /post/rhythmbox-playlist-folders, and it will be translated to /post/rhythmbox-playlist-folders, so it will work on any checkout.

To implement this solution, we will make some changes in a module and some changes in your site's theme.

First, the module. We need to have a module that implements hook_nodeapi. For all the sites I do, I always end up with some custom modifications, so let's say we have a module called "custom". (Technically, I could take the changes I'm about to present and release it as a module, but it is incomplete without the theme changes, and it doesn't seem like it should be a whole module release). In our custom module, I will implement hook_nodeapi:

function custom_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL) {
	switch($op) {
	case 'view':
		$node->content['body']['#value'] = preg_replace_callback(
			'/<([^>]*)(src|href)="([^"]*)"/i', 
			"_custom_twiddle_links", 
			$node->content['body']['#value']);
 
		break;
	}
}
 
function _custom_twiddle_links($matches) {
	$url = $matches[3];
	if (preg_match('|^[a-z][^:]*://|', $url)) {
		// It's an absolute url.  Return the whole thing as given.
		$retval = $matches[0];
	} elseif (strpos($url, "/") === 0) {
		// It's an absolute url on this host.  Fix it with the right base path.
		$retval = "<{$matches[1]}{$matches[2]}=\"".base_path().ltrim($matches[3],"/")."\"";
	} else {
		// It's a relative url.  Return the whole thing as given.
		$retval = $matches[0];
	}
 
	return $retval;
}

This will replace the links when displaying nodes.

There's still the problem of blocks. That's why we edit the site's theme.

We edit blocks.tpl.php to start with this:

<?php
/**
 * If a link starts with /, it should be relative to the base_path of the site,
 * not to the actual server root.
 */
if (!function_exists("_block_twiddle_links")) {
	function _block_twiddle_links($matches) {
		$url = $matches[3];
		if (preg_match('|^[a-z][^:]*://|', $url)) {
			// It's an absolute url.  Return the whole thing as given.
			$retval = $matches[0];
		} elseif (strpos($url, "/") === 0) {
			// It's an absolute url on this host.  Fix it with the right base path.
			$retval = "<{$matches[1]}{$matches[2]}=\"".base_path().ltrim($matches[3],"/")."\"";
		} else {
			// It's a relative url.  Return the whole thing as given.
			$retval = $matches[0];
		}
 
		return $retval;
	}
}
 
if ($block->module == 'block') {
	$block->content = preg_replace_callback(
		'/<([^>]*)(src|href)="([^"]*)"/i', 
		"_block_twiddle_links", 
		$block->content);
}
?>

This will fix the links for blocks.

That's the best I can do. This solution is not elegant. Perhaps there can be a a fix at the Drupal core level, so that we won't have to apply these dirty hacks. Perhaps this hack could be adjusted to have a token like [BASE_PATH], instead of working on all server-absolute links.

Perhaps there could even be a solution using the existing token module. Please tell me if you know of one.