Online PHP editor | refs for AUQNK

@ 2017-04-04T14:01:17Z

<?php
$arr = [
    1 => [
        1 => 4,
        5 => 7
    ],
    2 => [
        1 => 2,
        5 => 5
    ],
    3 => [
        1 => 2,
        5 => 5
    ],
    4 => [
        1 => 6,
        5 => 9
    ],
    5 => [
        1 => 6,
        5 => 8
    ]
];

$sum = array_reduce($arr, function($carry, $item){
    $carry += $item[5];
    return $carry;
});
echo $sum;