count() / array_sum() / range()

count(array, mode);

array_sum(array);

array_product(array);

// Generates a sequential array.
range(start, end, step);

// Shuffles the elements of an array in random order.
shuffle(array);

// Returns one or more random keys from an array.
array_rand(array, count);

count.php

<?php
$members = ['Kiryu Kazuma', 'Majima Goro', 'Akiyama Shun', 'Nishikiyama Akira'];
echo count($members); // Outputs "4".

// Calculate the sum of an array.
$prices = [150, 80, 300, 200];
echo array_sum($prices); // Outputs "730".

// Calculate the product of an array.
$nums = [2, 3, 4];
echo array_product($nums); // Outputs "24".

// Calculate the average.
$scores = [85, 92, 78, 95, 88];
$average = array_sum($scores) / count($scores);
echo $average; // Outputs "87.6".

// Generate a sequential array.
$one_to_ten = range(1, 10);
print_r($one_to_ten); // Generates an array from 1 to 10.

// Generate an array of even numbers using a step value.
$evens = range(2, 10, 2);
print_r($evens); // Results in [2, 4, 6, 8, 10].

// Generate an array of letters.
$alphabet = range('A', 'F');
print_r($alphabet); // Results in ['A', 'B', 'C', 'D', 'E', 'F'].

// Shuffle an array randomly.
$cards = range(1, 5);
shuffle($cards);
print_r($cards); // Elements are in a random order (changes every run).

// Pick a random element from an array.
$fighters = ['Kiryu Kazuma', 'Majima Goro', 'Akiyama Shun', 'Saejima Taiga', 'Nishikiyama Akira'];
$key = array_rand($fighters);
echo $fighters[$key]; // Outputs one random fighter name.

// Pick multiple random keys.
$keys = array_rand($fighters, 2);
print_r($keys); // Returns two randomly selected keys.

Running the code produces the following output:

php count.php
4
730
24
87.6
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
)
Array
(
    [0] => 2
    [1] => 4
    [2] => 6
    [3] => 8
    [4] => 10
)
Array
(
    [0] => A
    [1] => B
    [2] => C
    [3] => D
    [4] => E
    [5] => F
)
# shuffle() result is random. It changes every run. Example:
Array
(
    [0] => 3
    [1] => 1
    [2] => 5
    [3] => 2
    [4] => 4
)
Kiryu Kazuma
# array_rand() result is random. It changes every run. Example:
Array
(
    [0] => 0
    [1] => 3
)

Since PHP 7.2, passing a value that is neither an array nor a Countable object to count() triggers a warning. Avoid passing strings or numbers.

<?php
$members = ['Kiryu Kazuma', 'Majima Goro', 'Akiyama Shun'];
echo count($members); // Correct: outputs "3".

// Passing a non-array value triggers a warning in PHP 7.2+.
$name = 'Kiryu Kazuma';
// echo count($name); // Warning: count(): Parameter must be an array or an object that implements Countable

shuffle() modifies the original array directly and re-indexes all numeric keys starting from 0. Using it on an associative array destroys the original keys.

<?php
$fighters = [
	'a' => 'Kiryu Kazuma',
	'b' => 'Majima Goro',
	'c' => 'Akiyama Shun',
];

shuffle($fighters); // Keys are re-indexed to 0, 1, 2.
print_r($fighters);
// Array
// (
//     [0] => Majima Goro
//     [1] => Kiryu Kazuma
//     [2] => Akiyama Shun
// )
// The original keys 'a', 'b', 'c' are gone.

array_rand() returns the key(s) of the randomly selected element(s), not the values themselves. You need to use the returned key to access the value in the array.

<?php
$fighters = ['Kiryu Kazuma', 'Majima Goro', 'Akiyama Shun', 'Nishikiyama Akira', 'Saejima Taiga'];

$key = array_rand($fighters);
echo $key; // Outputs a key (e.g., "2")
echo $fighters[$key]; // Use the key to get the value (e.g., "Akiyama Shun")

// Getting multiple keys
$keys = array_rand($fighters, 2);
foreach ($keys as $k) {
	echo $fighters[$k] . "\n"; // Use each key to access the value.
}

Random selection logic

Randomly picking one or more members from a list.

<?php
function drawLottery(array $members, int $count = 1): array {
	$keys = array_rand($members, min($count, count($members)));
	$results = [];
	if (!is_array($keys)) {
		$keys = [$keys];
	}
	foreach ($keys as $k) {
		$results[] = $members[$k];
	}
	return $results;
}

$members = ['Kiryu Kazuma', 'Majima Goro', 'Akiyama Shun', 'Nishikiyama Akira', 'Saejima Taiga'];
$winners = drawLottery($members, 2);
foreach ($winners as $winner) {
	echo $winner . " won!\n";
}

sample_lottery.php

php sample_lottery.php
Akiyama Shun won!
Saejima Taiga won!

Array statistics

Getting the total, average, max, and min of an array all at once.

<?php
$scores = ['Kiryu Kazuma' => 95, 'Majima Goro' => 88, 'Akiyama Shun' => 72, 'Nishikiyama Akira' => 91, 'Saejima Taiga' => 84];

echo "Count: "   . count($scores) . "\n";
echo "Total: "   . array_sum($scores) . "\n";
echo "Average: " . (array_sum($scores) / count($scores)) . "\n";
echo "Max: "     . max($scores) . "\n";
echo "Min: "     . min($scores) . "\n";

sample_stats.php

php sample_stats.php
Count: 5
Total: 430
Average: 86
Max: 95
Min: 72

count() can be used not only on arrays but also on objects that implement the Countable interface. Since PHP 7.2, passing a value that is neither an array nor a Countable object triggers a warning. The alias sizeof() also exists, but count() is more commonly used.

array_sum() also works on the values of associative arrays. Non-numeric values are treated as 0. Combining array_sum() and count() lets you calculate an average.

range() can generate sequences of strings as well as numbers. Passing a negative step value creates a descending array.

shuffle() modifies the original array in place and re-indexes keys starting from 0. array_rand() returns keys, not values, so you need to use the returned key to access the corresponding array element. For aggregating array values, see array_reduce().