Anybody knows How to easily calculate X days moving average for a 365days data. any source available?

Can you clarify?

What is an "X days moving average"?
What is "365 days data"?

I don't really get it. Do you mean that you have data of something's movement over 365 days, and you want to calculate it's avarge movement over a given number of days?

In general, you calculate avarages by adding the values together and dividing by the number of terms. Avarge of [2, 17, 3, -4, 0, 6] is (2+17+3-4+0+6)/6 = 24/6 = 4

thank you guys, you are right, I need to clarify it a little bit.
1. I saved data into a array, data[] (say 365 days data).
2. I need print X days average line on the screen.
3. I want to create a FUNCTION to do that.
4. user can define X=5 days or 10 days whatever they want.

the math is there, I knew that, but I am new to PHP, I need some help to make that FUNCTION to calculate.

my thought is:
first, take last X days data, dividen them by X, then sum them. save it to a array. then do second .......

but not get it yet, any open source available?
Thanks.

So you want to compute the average of the values in data[] over a certain interval?

PHP Code:

function computeAverage($data, $begin, $end)
{
     $total = 0;
     for($i = $begin; $i < $end; $i++)
     {
           $total += $data[$i];
     }
     return (float) $total / ($end - $begin);
}