This is PHP and the syntax is very similar to C. If you see the link I provided, it wont be very difficult for you to decipher the working logic. sign() is a server side function which is taking $txSkeleton & $privateKeys variables as input and returning the signed data. But, if I could sign using PHP itself, I could avoid this step and directly push the signed Tx. I hope, someone, who knows PHP, chime in and point me to a code that allows me to do so...
Okay - then I hope the OP will explain his misleading point (hopefully it isn't a scam but it could be).
Well... blockcypher is definitely not a scam. blockcypher API is also used by services like ShapeShift.io. blockchain.info needs your private key/password too to send a Tx. This has become the de-facto rule for small bitcoin app devs and most do not bother much about this (well they'll tell you lots of security stories though). I have used blockchain.info before and none of my faucets ever got hacked. The thumb rule is to keep low amount in the hot wallet. But, as I am preparing for a bigger project I was exploring for an API that offers better security.