Displaying avg reading in seven days interval - php

Question

Given an array and I need to to display the average after every seventh row
Array
(
[0] => Array
(
[date] => 01-03-2015
[site_id] => 1
[starting_reading] => 567
[close_reading] => 567
)
[1] => Array
(
[date] => 03-03-2015
[site_id] => 1
[starting_reading] => 567
[close_reading] => 567
)
[2] => Array
(
[date] => 08-03-2015
[site_id] => 1
[starting_reading] => 567
[close_reading] => 567
)
)
Now what i need, is to display all avg reading in 7 days like:
1 to 7
--------------------- avg=close-start----------
8 to 14
--------------------- avg=close-start----------
15 to 21
--------------------- avg=close-start----------
22 to 28
--------------------- avg=close-start----------
29 to 31
--------------------- avg=close-start----------
date starting_reading close_reading
01-03-2015
03-03-2015
--------------------- avg=close-start----------
08-03-2015
--------------------- avg=close-start----------

Answer 1

//$arr is as the array you described
foreach($arr as $k => $v){
//$k will be some integer 0...count($arr)-1 assuming a 'normal' index
//$v is your child array, where you can access attributes such as $v['date']
//every seventh row can be done in a number of ways, the easiest way is:
if($k % 7 == 0){
//then show new line. This will happen every time the number divides into seven. 0, 7, 14, 21... etc.
var_dump($v); will output your child of the seventh (multiple) item
}
}
Including your example for dates and averages assuming array is correctly formatted
//$arr is as the array you described
$close = 0;
$start = 0;
foreach($arr as $k => $v){
//$k will be some integer 0...count($arr)-1 assuming a 'normal' index
//$v is your child array, where you can access attributes such as $v['date']
//every seventh row can be done in a number of ways, the easiest way is:
if($k % 7 == 0){
$close = 0; //reset close
$start = 0; //reset start
}
$close += (int)$v['close_reading'];
$start += (int)$v['starting_reading'];
if(($k + 1) % 7 == 0){ //this is the last row, 6, 13, 20 etc.
echo ($k-5).' to '.($k+1);
echo 'Average: '.(($close - $start) / 7);
}
}