Backdoors in script

Hello bidders, I need someone who knows how to remove a backdoor of a script already installed. the script does not have a ioncube files and was working perfectly until I a backdoor shutdown the site, so i need someone exper in php backdoors issue, someone who did this work previously, please don't waste my time and this is a little issue don't bid a higest bid (like 30$ or 50$ max), i need you put in Inbox this word (backdoor) this ways i will know that you read the entire description of the project. Thx