Won't work. The content isn't PHP, so PHP won't do it's thing to your content. In other words the content is just 'stuff' that your server will process (renderers for example) and spit out as part of your page, but it isn't capable of actually telling your server to do more stuff.

A workable solution is to do a little hacking and get iframe working in the posts (you can search here... it's been solved several times ). When you do your hack be sure to add the attributes you will need for the kind of display you are seeking (for example, it's useful to be able to set frameborder to "0" and scrolling to "no," when you wish what you are "including" to appear invisibly embedded in the post). You can then code whatever you wish into a webpage hosted in another directory on your server. Then you do the <iframe> in any post "calling" that webpage, which has your desired "othercontent.php" included there (and hence now displayed in your post).

Ok, thanks both of you... I estimated after trying the php-include that iFrames will be my next solution... I´ll search for it...