Script for trading short/sell (Arbitrage)

Developed in php the script trough api get the Ask and Bid of exchange with volume and store in db mysql (table_data) The script calculate the margin and if he bigger than one defined make a Buy to book1, and Short Sell to book 2. When the margin get lower he close the trading, sell to book 1 , and buyback the book2. The script need to support at least 1 exchange that allow short sell. In the first stage i need only two exchange : Kraken for buy Cex for short selling however script need to manage every aspect of order, check status. For every exchange, in a separate file need to be stored of course privatekey and secrect key and also comission fee. If you want know more about this concept search blackbird crypto on google. We need to check more than 1 pairs but for now only BTC/USD, and we open only one trade (no more trade open at the same time) In this first stage only two exchange, however the project must be build to be implemented in future. Developer must have some experience on trading and short selling.