Mining without using client Is there a way to mine bitcoins without installing a client, that is can I do it in PHP or Node.js by adding some libraries etc which replicate what the bitcoin client would do(more or less)?
You probably want this:

http://pastebin.com/ZYMNFAXt

It is a BTC miner that works in JS.  I took it from bitcoinplus.com

I don't think that this is economically feasible though - cpu mining is a total waste - unless you're looking to do something malicious with the code like having others use your tools that also happen to utilize CPU power to mine for btc underneath - which by the way is a sure fire way to get your software banned and shunned at large.  What you describe sounds like something deployed in a botnet or malware scheme - perhaps a bad android modded rom.