PHP Exercises: Compute sum of the prime numbers less than 100
PHP: Exercise-37 with Solution
Write a PHP program to compute the sum of the prime numbers less than 100.
Note: There are 25 prime numbers are there in less than 100.
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97 and sum of all these numbers is 1060.
Sample Solution: -
PHP Code:
<?php
$primes = array();
$is_prime_no = false;
for ($i = 2; $i<100; $i++) {
$is_prime_no = true;
for ($j = 2; $j<=($i/2); $j++) {
if ($i%$j==0) {
$is_prime_no = false;
break;
}
}
if ($is_prime_no) {
array_push($primes,$i);
}
if (count($primes)==100) {
break;
}
}
echo array_sum($primes)."\n";
?>
Sample Output:
1060
Flowchart:
PHP Code Editor:
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PHP: Tips of the Day
How to Sort Multi-dimensional Array by Value?
Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:
Example:
function sortByOrder($a, $b) { return $a['order'] - $b['order']; } usort($myArray, 'sortByOrder');
Starting in PHP 5.3, you can use an anonymous function:
usort($myArray, function($a, $b) { return $a['order'] - $b['order']; });
And finally with PHP 7 you can use the spaceship operator:
usort($myArray, function($a, $b) { return $a['order'] <=> $b['order']; });
To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.
usort($myArray, function($a, $b) { $retval = $a['order'] <=> $b['order']; if ($retval == 0) { $retval = $a['suborder'] <=> $b['suborder']; if ($retval == 0) { $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder']; } } return $retval; });
If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual
Ref : https://bit.ly/3i77vCC
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