I have the following code that case-insensitively groups associative elements in a flat array and sums the related values, but I don’t really understand how it works.
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 does it identify the same key of array to sum them (because keys position is dynamic)?
3
Answers
This means that if
keyortesthas no value, assign the value 0.For example,
$array = ['KEY', 'TEST' => 3, 'Test' => 10, 'Key'=> 2];The value of
KEYwill be 0.The
$sums[$key]is the sum of same elements.$sums[$key] + $valmeans add the previous sum value to the new element value.This code summing by uppercase keys group.
First step: checked the key exists. If not exists then fill with initial zero value. This case occurs once for per key (base of group). It is necessary so that the key’s non-existence does not pose a problem in the next step.
Second step: adds the value to the existed key container:
$sumsstarts as an empty array, but we’re trying to add numbers to it. If we try to add a number to$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.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
$keyin$sums[$key]is going to be either ‘TEST’ or ‘KEY’ in this code.