Accumulating Array Elements in PHP Loops

Let's use a loop to find the sum of the array elements:

php<?php
  $arr = [1, 2, 3, 4, 5];
  $res = 0;
  
  foreach ($arr as $elem) {
    $res += $elem;
  }
  
  echo $res;
?>

Задание 1

Given an array:

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

Find the sum of the elements of this array.

Задание 2

Given an array:

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

Find the sum of the elements that are even numbers.

Задание 3

Given an array:

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

Find the sum of the squares of the elements of this array.

Задание 4

Given an array:

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

Find the product of the elements of this array.