Error When Inserting A ' Into Mysql Text Field

I'm using the below code to insert some text fields from a form into a database. I've noticed that if we type something using a ' (i.e we're all going out for the day) in the text field then we get a insert error back from mysql saying it can't insert into the text field. I kind of think I know what the problrem is but need someone in the know to clear it up for me ....