I have associative array.Operation of the below code is that it will sum all the array index’s value which key is similar, but i did not understand how it operated.

function add_array_vals($arr) { $sums = []; foreach ( $arr as $key => $val ) { $key = strtoupper($key); if ( !isset($sums[$key]) ) { $sums[$key] = 0; } $sums[$key] = ( $sums[$key] + $val ); } return $sums; } $array = ['KEY' => 5, 'TEST' => 3, 'Test' => 10, 'Key'=> 2]; $sums = add_array_vals($array); var_dump($sums); //Outputs // KEY => int(7) // TEST => int(13)

i have problem in two portion of above code one is:

if ( !isset($sums[$key]) ) { $sums[$key] = 0; }

another is:

$sums[$key] = ( $sums[$key] + $val );

In this portion,how it identify the same key of array to sum them because keys position is random.

It will be really helpful if anyone clarify it.

## Advertisement

## Answer

if ( !isset($sums[$key]) ) { $sums[$key] = 0; }

`$sums`

starts as an empty array, but we’re trying to add numbers to it. If we try to add a number to `$sums[$key]`

that isn’t initialized yet, we’ll get an error, so we initialize it by setting it at zero the first time we encounter it.

$sums[$key] = ( $sums[$key] + $val );

This is the second part of the previous line. `$sums[$key]`

is at this point either zero, thanks to the previous line, or an integer, because we’ve encountered it before in the loop.

The `$key`

in `$sums[$key]`

is going to be either ‘TEST’ or ‘KEY’ in this code.

**10**People found this is helpful