Question

The headline says it all: Is there a vertical sum function in php that adds a (sub)array value over the entire array, like this:

 // pseudo code that would return the sum of "income" for all days of the year
 // for example
 vertical_sum($array[$day_of_year]["income"]);

Answer 1

Native function? Not exactly, but array reduction can help:

$array = array(
    array('income' => 1), //day 1
    array('income' => 3), //day 2, etc
    array('income' => 6),
    array('income' => 7)
);
echo array_reduce($array, function($curr_total, $this_val) {
    return $curr_total + $this_val['income'];
}, 0); //17