Forms securing on website / Minor glitch fixing

Good evening, Our website recently suffered an attack from a vulnerability found in the registration form. I then investigated it further and it seems that are various issues surrounding the forms on our website. We need a PHP expert who can secure the forms for us to protect us from these sort of exploits, for example by banning special characters from being entered in the forms other than where relevant. There is a registration form, log in form, profile, payouts and upload forms that need securing. To someone with knowledge in the area this job will be a piece of cake. There is also a problem with our script as when a user uploads a file containing special characters for example an apostrophe ('), our system produces an error wherever it attempts to call it. Low bids will be favoured. Also, payments cannot be made until the 28th however I would like work to be commenced ASAP as the vulnerabilities pose a threat in the meantime. Only bid if you are happy to work under these circumstances.