Graphing the connections between my blog posts
I love ripping off good ideas from other people's blogs. I was reading Alvaro Graves-Fuenzalida's blog when I saw this nifty little force-directed graph:
In this case, I can see that the posts about Small Gods and Pyramids both share the tags of Discworld, Fantasy, and Book Review. But only Small Gods has the tag of Religion.
Internal links back to the Post is slightly trickier. WordPress doesn't save relational information like that. Instead, we get the Post's URl and search for that in the database. Then we get the post IDs of all the posts which contain that string.
Searching for links is slightly more complex. The easiest way is to load the HTML into a DOMDocument, then extract all the anchors. All my blog posts start /blog/YYYY so I can avoid selecting links to tags, uploaded files, or other things. Your blog may be different.
The ID of each post can be found with the url_to_postid() function. That means we can re-use the earlier code to see what tags those posts have.
