Adding a filter for only specific pages

[dashifen]

Greetings,

I'm working on a plugin that adds some shortcodes. When those shortcodes are present in the content, I'd like to change the way the title is printed for the page or post. The way I'm handling it now is to add a filter on both the_title and wp_title. Then, I get the content of the post/page from within the filter's function and manually look for the shortcodes that within that content. If I find them, I finally change the way the title looks and if I don't, then I do nothing.

It's working successfully but it seems like an awful lot of work, but I suspect it might be necessary since the title is printed before the content is handled which is where the system first encounters the shortcodes.

Is there an easier way?

Thanks,
Dash

[dashifen]

An update: doing it the way I described above using the code below, means that the titles get changed in the site's menu when you're on one of the plugin pages, too. The menu is printed using wp_list_pages(). Here's the code I'm trying to use:

 
add_filter("the_title", "title_filter");
function title_filter($title) {
  global $post;
  if(strpos($post->post_content, "[XYZ]")===false) return $title;
  return "Whee!";
} 
  

The shortcode [XYZ] is replaced with a few shortcodes and, eventually, I think I'll switch it from calls to strpos() to a regular expression so that it's not too repetative, but I'm trying to keep the PHP simple for the moment.

The altered title wouldn't be "Whee!" either, that's just for the purposes of this example.

[dashifen]

Update #2: I've fixed the menu problem after stumbling over the in_the_loop() method. The above PHP has been altered to use this conditional:

 if(!in_the_loop() || preg_match(...)) return $title 
  

That makes things work out pretty well.

[Ryan]

Tricky problem. I recall their being another thread around here on this topic but I can't recall where it is in the forum. Maybe someone else will recall.

[Otto]

The basic problem is that you're using shortcodes in the wrong way. They were designed to be in the content and to be replaced by something, not to trigger other actions elsewhere on the page.

You might look for another way to detect when you need to adjust the title, instead of relying on the user to insert a shortcode onto the post.

[Ryan]

The basic problem is that you're using shortcodes in the wrong way. They were designed to be in the content and to be replaced by something, not to trigger other actions elsewhere on the page.

I can see where you are coming from, but I can also see how having shortcodes load stuff outside of the_content() is useful.

Something like Contact Form 7 springs to mind. It would make sense for it to only load it's JS and CSS files on pages in which it's shortcode is used, but instead it just loads them across the entire site. The only alternative I've come up with myself is to specify separately where you want the CSS and JS to load, but that's not exactly the most elegant way to do it as it requires two actions to achieve it whereas if it could be done via the shortcode then it would only take one.


I wish I could remember where I'd read how to do this. It's definitely possible, albeit my recollection is that it was rather awkward way of achieving something so trivial.

EDIT: My memory banks are coming back a little now. There were a bunch of methods posted, one required parsing the_content() twice to detect the shortcode, the other didn't (and hence was much more efficient) - or maybe it did parse it twice but did it in a more efficient way??? Damn fuzzy memory :(

[Otto]

Something like Contact Form 7 springs to mind. It would make sense for it to only load it's JS and CSS files on pages in which it's shortcode is used, but instead it just loads them across the entire site.

I've never understood why people want to bother with this. It doesn't save you any time to not load the JS and CSS, even if they're not being used. Not really. Browser caching eliminates the differences here.

And if you're one of those people who use trickery to combine CSS and or JS dynamically into a single request, then not loading things is actually actively detrimental to the speed of your site, since everything else now has to load twice.

If you really, really want to do it, just examine the $post->post_content yourself for the shortcode, then have your shortcode processing function do nothing but return an empty string to eliminate the shortcode from displaying.

[Ryan]

Caching does not work when someone visits your site for the first time though. Having 20 something plugins all loading their own CSS and JS files is a real killer for load time (not that I have that many loading, but some people do).

What I actually intend to do eventually on my own site is to just copy and paste all the CSS and JS I need into single files, compress the hell out of them and serve them all as a single file. I wouldn't do it dynamically for the reason you mentioned.

If you really, really want to do it, just examine the $post->post_content yourself for the shortcode, then have your shortcode processing function do nothing but return an empty string to eliminate the shortcode from displaying.

Er, wouldn't you need to load a loop prior to wp_head() firing for that to work? Or am I misunderstanding something here?

[Otto]

Er, wouldn't you need to load a loop prior to wp_head() firing for that to work? Or am I misunderstanding something here?

The OP was talking about modifying the_title(), which would be already in the loop. If you wanted to insert CSS or JS, then you'd need to start the loop, grab the data, then use rewind_posts to roll the loop back. This is simpler than it sounds. I use code like this in SFC:

 function sfc_share_meta() {
    $excerpt = '';
    if (is_singular()) {
        the_post();
        rewind_posts(); 
        $excerpt = strip_tags(get_the_excerpt());
?>
<meta name="stuff" />
...