PHP - Template Method Pattern And Process Interruption

Hey guys.  So I'm trying to write a script that replaces footnote citations in one format with footnote citations in another format.

For example, the text will read:   "Then he went down the street.[1] That is where the police found him [2].  They immediately arrested him at the house. [3]"

And I would like the script to find the [ #] strings and replace them with {#} ... so that the string reads:
"Then he went down the street.{1} That is where the police found him {2}.  They immediately arrested him at the house. {3}"

Note that there will be double, and even tripple, digit footnotes, so the script has to be able to recognize [##] or [###] and replace the brackets with {} accordingly.

I'm not really sure how to do this, since the "pattern" is constantly changing depending on the number between the brackets.  Ideas?

Thanks!

 

My script has 3 classes (that are relevant to this discussion): DB, User and Validate. They are all in independent files and loaded automatically, when required, by an autoloader.
Both the User class and the Validate class have a private variable $_db which is instantiated by their class constructor: $this->_db = DB::getInstance();
At the top of the script I declare new instances: $user = new User(); and $validate = new Validate();
I then call a method in $user: $found = $user->findInUsers ( .... )
From within the findInUsers method I then want to call the query method in the DB class. My problem is that I can't find a way to do this that works.
I have tried $this->_db->query( ... ), $_db->query( ... ), but neither works.

The error messages I am getting a
An error occurred in script '/srv/http/classes/User.php' on line 42: Undefined variable $_db
Uncaught Error: Call to a member function query() on null in /srv/http/classes/User.php:42

Any pointers as to what I am doing wrong, or what I should be doing, would be most welcome.

How to make "hints" as dynamic varaible:

Hey Guys. I am learning about the Enterprise pattern, and to me it seems like its the same as the MVC pattern (which I learned about) Do they work the same??   For those who know Martin Fowler's Patterns of Enterprise Application Structure, that is what I am referring to as the enterprise pattern
Edited by eldan88, 13 October 2014 - 10:24 AM.

So I was stumbling around with Repositories and Interfaces and got a decent grasp on it. However, I started running into abstraction and started to implement a little bit of the Factory design.   How often is this typically used? It seems like I should be using  Factory with 90% of my Repositories since there are different types of Items, Tutorials, Random Events, etc.   Items - Food - Weapon - Toy   Tutorials - Newbie - Farming   Random Events - Coin Giving - Item Giving - Item Draining   Things like this... so all of them have similar methods involved. So they each have a base method, for example.. an Item child class would always have the use() method and a factory would determine which kind of object to initiate from your controller just from the item model being passed through. So therefore you can call use() on the repository instance it returns. Then I was moving onto my tutorials and random events and it just seemed very similar.   So in most cases, will factories be a huge plus? Just wanted some general opinions from the PHP developers =) Thanks!