How to edit content using PHP CODE?

Hi,

I want to do this:

1. Create content.
2. User enters in information.
3. Modify the information before it gets outputted to the user.

Example:
Field is Address.
User enters in address.
Now everytime that content is shown it is auto linked to google maps.

How do I do this with the PHP code section? I do not know what is the variable to call and what to return.

The example given is this, but it doesnt help at all:
array(
  0 => array('value' => value for value),
  // You'll usually want to stop here. Provide more values
  // if you want your 'default value' to be multi-valued :
  1 => array('value' => value for value),
  2 => ...
);

Using devel.modu

Can someone please clarify?