editing php reservations script

i want to hire someone to help in editing PHP scripts for reservations, if i experience difficulty in managing the script, i am sure i will need, not right now but for when i have an issue. i just want to make sure i will have someone capable to handle and resolve issues, so i need someone who knows very good how to edit a reservation script. it requires good very good knowledge of PHP & mySQL. The others JS+ are optional and not necessary. but i would like the person i will hire to work via my PC so that i see what he or she does, as i cannot trust someone who i do not know and give them login details, and by the how, how long they will work i will pay. i repeat, i am sorry but i cannot give sensitive personal login details as in the past i passed through bad experience when someone said that i need to have trust. that is why this is important.