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1. ermitanyo
   Member
   Posted 3 years ago #

   Here's the code. Help please.

   <?php
   $prevpost = substr(previous_post_link('<li>%link</li>', '&laquo; %title'),0,14);
   echo $prevpost;
   if (strlen($prevpost) > 14 ){
   echo ' ...';
   }
   ?>

2. frame25
   Member
   Posted 3 years ago #

   I've been trying to solve the problem of too-long-titles myself.

   The problem you're having is that the previous_post_link function echoes its output directly. It doesn't return a string for substr to then chop up and echo manually. The moment previous_post_link gets called in your code, BOOM, it gets echoed. So it's not being processed. A lot of WordPress functions are like this. If you want to capture the output to shorten it, you have to use output buffering, like this:

   ob_start();
       next_post_link('%link');
       $next_post_link = ob_get_contents();
       ob_clean();
       previous_post_link('« %link');
       $previous_post_link = ob_get_clean();

   Now you have the links output as variables you can process, and nothing has been echoed to the screen yet.

   But there still remains a problem. If you use the above code, the content of the $next_post_link variable is HTML and wrapped in an A tag. So you'll have succesfully captured, for example:
   « Previous Post Title
   Now if you try to run substr on that and add ellipses, you'll be butchering the HTML and breaking the page. It'll create something like:
   « Previous Post Title<...
   So you can see, it breaks the closing A tag and doesn't actually shorten the title. So if you did this you'd have to use a regular expression (like preg_replace) to find and shorten the title inside the tag. (WordPress should really add an argument to the functions to allow you to shorten it.)

   The output buffer + regular-expression approach is the only one I've found so far, and I haven't implemented it yet because regular expressions are a colossal pain in the ass.

3. frame25
   Member
   Posted 3 years ago #

   Darnit, the comment system converted some of what I typed above to code, so let me try again starting with the paragraph "But there still remains a problem:"

   *snip*

   But there still remains a problem. If you use the above code, the content of the $next_post_link variable is HTML and wrapped in an A tag. So you'll have succesfully captured, for example:
   &laquo; <a href="http://www.example.com/prevpost">Previous Post Title</a>
   Now if you try to run substr on that and add ellipses, you'll be butchering the HTML and breaking the page. It'll create something like:
   &laquo; <a href="http://www.example.com/prevpost">Previous Post Title<...

   */snip*

4. Otto
   Tech Ninja
   Posted 3 years ago #

   A simpler way would be to notice that previous_post_link has a filter on it, so you can define a function to do what you like with it.

   function my_filter($post_link_string, $link);
   // modify $post_link_string here as you see fit, then return it.
   // $link contains just the link, if you need to know that.
   return $post_link_string;
   }
   add_filter('previous_post_link','my_filter');

   No need to use output buffering.

   Same goes for next_post_link, BTW.

5. frame25
   Member
   Posted 3 years ago #

   I was just about to post my regex solution to this, but that's a brilliant find. I had no idea such a filter existed.

   One problem though: there doesn't seem to be an actual 'previous_post_link' filter in the API (http://codex.wordpress.org/Plugin_API/Filter_Reference), just one for 'post_link' -- which the documentation seems to suggest would apply to all permalinks, which is not what I want. Am I wrong here? The filter documentation is:

   post_link
   applied to the calculated post permalink by the get_permalink function, which is also called by the the_permalink, post_permalink, previous_post_link, and next_post_link functions. Filter function arguments: permalink URL, post data list.

6. frame25
   Member
   Posted 3 years ago #

   Okay, I found out that the filter DOES exist, it's just not on the Plugin API page. It's here:
   http://adambrown.info/p/wp_hooks/hook/%7B$adjacent%7D_post_link

   So, thank you Otto! Now here is my solution:

   function filter_shorten_linktext($linkstring,$link) {
   	$characters = 33;
   	preg_match('/<a.*?>(.*?)<\/a>/is',$linkstring,$matches);
   	$displayedTitle = $matches[1];
   	$newTitle = shorten_with_ellipsis($displayedTitle,$characters);
   	return str_replace('>'.$displayedTitle.'<','>'.$newTitle.'<',$linkstring);
   }
   
   function shorten_with_ellipsis($inputstring,$characters) {
     return (strlen($inputstring) >= $characters) ? substr($inputstring,0,($characters-3)) . '...' : $inputstring;
   }
   
   // This adds filters to the next and previous links, using the above functions
   // to shorten the text displayed in the post-navigation bar. The last 2 arguments
   // are necessary; the last one is the crucial one. Saying "2" means the function
   // "filter_shorten_linktext()" takes 2 arguments. If you don't say so here, the
   // hook won't pass them when it's called and you'll get a PHP error.
   add_filter('previous_post_link','filter_shorten_linktext',10,2);
   add_filter('next_post_link','filter_shorten_linktext',10,2);

   You simply place this in your theme folder's "functions.php" file and it will start working. Change $characters = 33; to the number of characters you want it to cut off at. I may write a plugin to do this, too; we'll see.

7. Otto
   Tech Ninja
   Posted 3 years ago #

   The documentation, as you have discovered, is incomplete. I suggest referring to the actual code in WordPress instead, it's easier to understand.

8. frame25
   Member
   Posted 3 years ago #

   I put together a plugin to automate this fix. I applied for an account to post the plugin officially but haven't heard back yet, so for now, find the plugin and instructions and screenshots here:
   http://www.filmtraveler.com/2008/11/18/wordpress-plugin-shorten-link-text/

   Thanks for your help, Otto, in recommending the filter!

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