rendition: There is a difference between linking to posts from other blogs of similar content, and republishing someone elses feeds onto your site.
You can do this by writing your own posts saying something like "Hey, So and So over at bla bla.com recently wrote about...eg..go check it out, good read"
If you simply set it up so that your blog republishes every post from another blog, then you're actually not sharing, it isn't WIN, WIN, WIN. You're in fact stealing traffic from the other blog. Why read the original blog, when I can read it on yours?
Furthermore, you MUST ask permission from the feed owner before you attempt anything of this nature. Not only is it common courtesy, but a cardinal rule of blogging. Failure to do so is oft simple copyright infringement.
Blogs don't have RSS feeds so others can republish their content. Blogs have RSS feeds so that people can read their content from an RSS reader or otherwise as it makes their content more accessible to the individual reader.
Want to share content, make a WIN WIN situation? Publish your OWN post with a link and blurb everytime you see an article you like on another site.
Publishing others feeds is not the answer to your needs.
cluelessone: I'm not a PHP expert, I'll hunt around for an answer to your problem. For your purpose, I'm willing to help.