php Getting sum arrays, but have "Notice" Undefined offset: 0

Question

Creating an array and diving it in 3 other arrays with the PHP function array_chunk()

$sumArray = array ( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 );
$reviews_count = 4;
$sum_divided_array = array();
$sum_divided_sub_array = array();
/* Dividing the array in 3 other arrays */
$divided_array = array_chunk($sumArray, $reviews_count); 

foreach ($divided_array as $key_divided_sub_array => $sum_divided_sub_array) { 
    for ($i = 0; $i <= (count($sum_divided_sub_array) -1); $i++) {
        if(isset($sum_divided_sub_array[$i])) {
            if(array_key_exists($i, $sum_divided_sub_array)) {
                $sum_divided_array[$i] +=  $sum_divided_sub_array[$i]; 
            }
        }                                               
    }    
}
print_r( $sum_divided_array );

You are trying to read-access `$sum_divided_array[$i]` without checking whether that index already exists. — 04FS, Feb 25 '19 at 14:09
Your two ifs seem to be checking the same thing in two different ways. You probably meant to check the array $sum_divided_array in the inner one … But you still need an else branch for that, otherwise you would not be doing anything with `$sum_divided_sub_array[$i]` at all in that case. — 04FS, Feb 25 '19 at 14:13
Possible duplicate of ["Notice: Undefined variable", "Notice: Undefined index", and "Notice: Undefined offset" using PHP](https://stackoverflow.com/questions/4261133/notice-undefined-variable-notice-undefined-index-and-notice-undefined) — devpro, Feb 25 '19 at 14:19

Andrii Filenko · Accepted Answer · 2019-02-25T15:02:30.583

The main error is that you missed checking if $sum_divided_array[$i] exists, before adding something to it, the right code would be:

<?php
        //Enter your code here, enjoy!

$sumArray = array ( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 );
$reviews_count = 4;
$sum_divided_array = array();
$sum_divided_sub_array = array();
/* Dividing the array in 3 other arrays */
$divided_array = array_chunk($sumArray, $reviews_count); 

foreach ($divided_array as $key_divided_sub_array => $sum_divided_sub_array) { 
    for ($i = 0; $i <= (count($sum_divided_sub_array) -1); $i++) {
        if(isset($sum_divided_sub_array[$i])) {
            if(isset($sum_divided_array[$i])) {
                $sum_divided_array[$i] +=  $sum_divided_sub_array[$i]; 
            } else {
                $sum_divided_array[$i] =  $sum_divided_sub_array[$i]; 
            }
        }                                               
    }    
}
print_r( $sum_divided_array );

If sum_divided_array is set, we are adding subarray value to it, if not, we are assigning current subarray to it.

My code works but it gives this "notice" with offset. Your code prints different result, I just want to sum the arrays according to those indexes. — Lucian Ardeleanu, Feb 25 '19 at 14:38

php Getting sum arrays, but have "Notice" Undefined offset: 0

1 Answers1