Optimization of Unnecessary Loop Iterations in PHP

In the following code, a certain programmer checks if the array contains the number 3:

<?php
	$arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
	
	$exists = false;
	foreach ($arr as $elem) {
		if ($elem == 3) {
			$exists = true;
		}
	}
	
	var_dump($exists);
?>

What's wrong with their solution? It seems like no unnecessary operations are performed in the loop. The problem, however, is that after it's determined that the number 3 is in the array - the loop still continues to run until the end of the array.

The most inefficient scenario would be if the number 3 is found somewhere at the beginning of the array, and the array itself has a length of, say, 1000 elements. That would result in a thousand useless extra loop iterations! Not optimal.

Let's optimize the code by stopping the loop in time:

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

The following code calculates how many array elements need to be added for the sum to become greater than 10. Perform optimization:

<?php
	$arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
	$sum = 0;
	$i = 1;
	
	foreach ($arr as $elem) {
		$sum += $elem;
		
		if ($sum <= 10) {
			$i++;
		}
	}
	
	echo $i;
?>

The following code outputs even numbers from a given range. Perform optimization:

<?php
	for ($i = 0; $i <= 100; $i++) {
		if ($i % 2 === 0) {
			echo $i;
		}
	}
?>

The following code outputs numbers divisible by both 2 and 3. Perform optimization:

<?php
	for ($i = 0; $i <= 100; $i++) {
		if ($i % 2 === 0 and $i % 3 === 0) {
			echo $i;
		}
	}
?>