Wat what point should I be putting them, at the start of the script or just before I use them.
Up to you, though defining a series of functions in one place makes it easier for one to refer to them.
This is especially so since you would expect to use the function more than once, otherwise it may be easier to incorporate the function directly into the caller.
As of PHP4 you can even define the function after you call it, as long as it is, eventually, defined.
Does it make any difference if the function definition is inside or outside of the conditional statement and if the use is inside the conditional statment?
There generally is no need to conditionally define functions.
One would conditionally call the required function instead, or implement the conditional within the function.
