Automatically generating custom field values in Wordpress

Question

I run a few side blogs that I sort of aggregate into my main blog. I use simplepie to parse the feeds from my other blogs, so the posts are being created automatically.

My typical post is layed out like this:

1. IMAGE
2. CONTENT/TEXT
3. HYPERLINK

What I'm looking to do is automatically grab the hyperlink, and insert it into a Custom Field. The custom field already exists in the post, but I need to insert the hyperlink contained in the post content as the value.

I would need just the link, without the html, so the value would be just a straight link - http://domain.com/fsdds

I know there are a number of plugins that accomplish this with images, but I haven't seen anything that will do it with anything else, like hyperlinks.

I posted this question over at the Wordpress forums and was told I'd have to parse the entire post content looking for the links, which I knew, the problem is I'm not too sure how to do that.

Thanks

Answer 1

I've been thinking about this myself and the solution has to be to run a function on the save_post action hook. Unfortunately this is undocumented in the Wordpress Codex and I haven't had time to look further afield yet.

Answer 2

Just stumbled upon this Function Reference/add post meta

Still need a way to grab the hyperlink from the post and and insert it as the $metavalue though.

Answer 3

This is the function that grabs the first image in a post:

function catch_that_image() {
      global $post, $posts;
      $first_img = '';
      ob_start();
      ob_end_clean();
      $output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
      $first_img = $matches [1] [0];

      if(empty($first_img)){ //Defines a default image
        $first_img = "/images/default.jpg";
      }
      return $first_img;
    }

you would just need to replace the first preg_match_all parameter to:

'/(https?://)?(www.)?([a-zA-Z0-9_%]*)\b.[a-z]{2,4}(.[a-z]{2})?((/[a-zA-Z0-9_%])+)?(.[a-z])?/'

Add the whole function to your functions.php, and call that function from your script. It should return the first link it finds in the post content.

Answer 4

---

Building on Anthony's answer, use the UPDATE POST META once you have your link...

Put this in your functions.php file:

function catch_that_link() {
      global $post, $posts;
      $first_link = '';
      ob_start();
      ob_end_clean();
      $output = preg_match_all('/(https?://)?(www.)?([a-zA-Z0-9_%]*)\b.[a-z]{2,4}(.[a-z]{2})?((/[a-zA-Z0-9_%])+)?(.[a-z])?/', $post->post_content, $matches);
      $first_link = $matches [1] [0];

      if(empty($first_link)){ //Defines a default image
        return 'no link found';
      }
      return $first_link;
    }

Then in your query loop, category file or whatever php file you would do the following

<?php 

$post_id = 13; //replace the number with the specific post
$meta_key = 'key_example' //replace with your custom field name
$meta_value = catch_that_link();

update_post_meta($post_id, $meta_key, $meta_value); 
?>