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How foreach loop work to sum value of same key in associative array

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.

JavaScript

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.

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Answer

JavaScript

$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.

JavaScript

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.

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