Optimization Through Built-in Functions in PHP

Suppose a programmer checks if the array contains the number 5:

php<?php
  $arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
  
  $exists = false;
  foreach ($arr as $elem) {
    if ($elem == 5) {
      $exists = true;
      break; // exit the loop to avoid unnecessary iterations
    }
  }
  
  var_dump($exists);
?>

I claim that there is something wrong with this code. What is it? We exit the loop after finding the number 3, right? The fact is, that built-in PHP functions always work an order of magnitude faster than similar custom code.

In our case, there is a function in_array that solves the given task - and we should use exactly this function:

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

Moral: before solving a task, always check if there is a built-in PHP function for its solution.

Задание 1

In the following code, a programmer finds the sum of array elements. Optimize this programmer's solution.

Here is the code:

php<?php
  $arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
  
  $sum = 0;
  foreach ($arr as $elem) {
    $sum += $elem;
  }
  echo $sum;
?>

Задание 2

In the following code, a programmer finds the product of array elements. Optimize this programmer's solution:

php<?php
  $arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
  
  $res = 1;
  foreach ($arr as $elem) {
    $res *= $elem;
  }
  echo $res;
?>