Custom Blocks & Inserts
 

I've been searching for over 30 minutes now and it's taking up way too much time; is there a simple way to just create PHP blocks and insert them into templates parts? I've seen recommendations for the vB CMS and vBulletin 4, but not 3.

Well, you can create a plugin for your php that creates a string with html, then edit the template and insert the ariable where you want the html to appear. The plugin hook location and the template name depend on exactly where you want it to appear.

You can create your own template and have your plugin code render that template to a string, then insert that in another template, if you prefer to generate your html that way.

Have a read of this: How to Include a PHP or HTML File