Diagonal difference of 2D array – PHP Given a square matrix, calculate the absolute difference between the sums of its diagonals.
For example, the square matrix arr is shown below:

The left-to-right diagonal = 1 + 5 + 9 = 15. The right to left diagonal = 3 + 5 + 9 = 17 . Their absolute difference is  |15 – 17| = 2.

Function description
Complete the diagnoalDifference  function in the editor below. It must return an integer representing the absolute diagonal difference.
diagonalDifference takes the following parameter:

• arr: an array of integers .
Input Format
The first line contains a single integer, , the number of rows and columns in the matrix .
Each of the next lines describes a row arr[I] , and consists of n space-separated integers arr[i][j] .
Output Format
Print the absolute difference between the sums of the matrix’s two diagonals as a single integer.
Sample Input
Sample Output
Explanation

The primary diagonal is:

Sum across the primary diagonal: 11 + 5 – 12 = 4
The secondary diagonal is:

Sum across the secondary diagonal: 4 + 5 + 10 = 19
Difference: |4 – 19| = 15

Note: |x| is the absolute value of x

Here, is the PHP function that will do this very easily. 