Projects in PHP

The following programming projects were found on various websites and seemed like they might be fun to try. Some are simple exercises, while others are complex brainteasers. In other words, I was looking for something to keep my mind busy. Feel free to try your hand at any of these before looking at my solution. Maybe you can find a better way. Enjoy!
All solutions on this page are in PHP. I will post solutions in other languages (i.e. C++, VB, etc...) when I have the time.
~ The Fibonacci Sequence ~
The Fibonacci Sequence is the list of numbers such that the first two numbers are ones (1) and each subsequent number is the sum of the previous two numbers (i.e. 1, 1, 2, 3, 5, 8, 13...). This is a pretty simple program to write. Here is my solution.
The numbers in the sequence get big quickly. You might want to put in a fault mechanism to stop when the numbers overflow. My solution stops when the 59th number in the sequence (956722026041) is reached, since PHP begins rendering the sequence in scientific notation after this.
~ Prime Numbers ~
A prime number is a number that has exactly two factors, itself and one. The smallest (and only even) prime is 2. Generating a list of primes less than a certain number is a time consuming task, therefore great for a programming project. Here is my solution.
I've limited my solution to the list of primes less than 1000. Any limit will do, but keep processing time in mind.
~ Base Conversion ~
The challenge here is to write an arbitrary base conversion utility. It should be able to convert a number in any base into another base. For example, 10 in decimal (base 10) is 1010 in binary (base 2). Here is my solution.
I've limited my solution to bases 36 or lower in order to simplify the list of possible digits to '0' through '9' and 'A' through 'Z'. Theoretically, this can be extended to any base by using multiple "digits" to represent each place, but that's overkill, don't you think?
~ The Quine ~
By definition, a quine is a program that produces its own complete source code as its only output. Sounds easy, doesn't it? Give it a try, then look at my solution.
You will need to view the page source to read the solution as it does not format as a visible HTML document. In IE, right-click and select "View Source" to see the page source code.