Question: I'm not asking for someone to code this for me, I just want a bit of advice and guidance.

Basically, I started learning jQuery last week and for my first project I want to make a countdown table.
e.g.

```
=====================
Time|Desc
---------------------
1.03|Item 1
---------------------
0.50|Item 2
=====================

```

Once the user starts the countdown the first item should be retrieved and used as a countdown, ie 1.03,1.02,1.01,1,0.59 in seconds (and should be updated live). Once that reaches zero, the row should be removed and the next item should be started as a countdown.

If anyone has had any experience building this or a countdown similar to this I would appreciate it. I've seen a few plugins but it seems overkill for my needs. All times will be less than an hour.

A few things; I'm struggling to understand is how I could initialize the second countdown as obviously the first row will take a few seconds to animate or remove. 

Any feedback, links, reading is appreciated I'm currently learning using a video course and will be finished in the next few days, but this is something outside of the class that I'm interested in.

Answer: 
Singletons have nothing to do with thread-safety. They are here to only have one instance of an object per process.

so, to answer your question: no, your script is not thread safe. php will start one process (not thread) for each call on the cli. both processes will create an instance of your class and both will try to write the file. 

the process to later write the file will win, and overwrite changes from the first process.
PHP is not threaded - it is process oriented. Each invocation of PHP (wether it be commandline or apache instance) is memory independent. 

Your singleton will only be unique to that one process.

(oh and instead of doing `$c=__CLASS__; $instance = new $c;` you should use 'self' like `$instance = new self();`. Same result, less fuss. Also be sure to set your \_\_construct() private/protected)