Arrays

<?php
$langs = ['PHP', 'SQL', 'JavaScript'];          // indexed: keys 0, 1, 2
$user = ['name' => 'Asha', 'age' => 31];        // associative

echo $langs[0], " and ", $langs[2], "\n";
echo $user['name'], " is ", $user['age'], "\n";
echo count($langs), " languages\n";

$user['city'] = 'Pune';                         // add a key
$user['age'] = 32;                              // overwrite a key
print_r($user);

// keys are normalised: "5" becomes int 5, true becomes 1
$mixed = ["5" => 'a', true => 'b', 1 => 'c'];
var_dump(array_keys($mixed));

<?php
$queue = ['a', 'b'];
$queue[] = 'c';                    // append
array_push($queue, 'd', 'e');      // append several
echo implode(" ", $queue), "\n";

$last = array_pop($queue);         // remove from the end
$first = array_shift($queue);      // remove from the front
echo "popped $last, shifted $first: ", implode(" ", $queue), "\n";

array_unshift($queue, 'z');        // add to the front
echo implode(" ", $queue), "\n";

$empty = [];
var_dump(array_pop($empty));       // null, no error

<?php
$nums = [10, 20, 30];
unset($nums[1]);
var_dump(array_is_list($nums));     // PHP 8.1: keys 0..n-1 in order?
echo json_encode($nums), "\n";      // a gap turns a JSON list into an object

$nums = array_values($nums);
var_dump(array_is_list($nums));
echo json_encode($nums), "\n";

<?php
$stock = ['pen' => 120, 'notebook' => 0, 'stapler' => 8];

foreach ($stock as $item => $qty) {
    $label = $qty === 0 ? "out of stock" : "$qty left";
    echo "$item: $label\n";
}

echo implode(", ", array_keys($stock)), "\n";
echo array_sum($stock), " items in total\n";
echo "Largest: ", max($stock), "\n";
echo array_key_first($stock), " .. ", array_key_last($stock), "\n";
print_r(array_count_values(['php', 'sql', 'php', 'go', 'php']));
print_r(array_combine(['a', 'b'], [1, 2]));

<?php
$prices = [120, 45, 300, 80];

$withTax = array_map(fn($p) => $p * 1.18, $prices);
echo implode(" ", $withTax), "\n";

$cheap = array_filter($prices, fn($p) => $p < 100);
print_r($cheap);                        // keys 1 and 3 are kept!
echo implode(" ", array_values($cheap)), "\n";

$total = array_reduce($prices, fn($carry, $p) => $carry + $p, 0);
echo "Total: $total\n";

// filter by key, or by key and value
$user = ['name' => 'Asha', 'password' => 'x9', 'city' => 'Pune'];
$safe = array_filter($user, fn($k) => $k !== 'password', ARRAY_FILTER_USE_KEY);
echo json_encode($safe), "\n";

// no callback: drops every falsy value ("", 0, null, "0", false)
echo json_encode(array_values(array_filter(['a', '', null, 'b', 0]))), "\n";

<?php
$scores = ['Ravi' => 91, 'Asha' => 72, 'Kiran' => 85];

$copy = $scores;
sort($copy);                         // values only, keys lost
echo json_encode($copy), "\n";

$copy = $scores;
arsort($copy);                       // by value, high to low, keys kept
echo json_encode($copy), "\n";

$copy = $scores;
ksort($copy);                        // by key
echo json_encode($copy), "\n";

$users = [
    ['name' => 'Ravi', 'age' => 27],
    ['name' => 'Asha', 'age' => 31],
    ['name' => 'Kiran', 'age' => 27],
];
// by age ascending, then name ascending
usort($users, fn($a, $b) => [$a['age'], $a['name']] <=> [$b['age'], $b['name']]);
echo implode(", ", array_column($users, 'name')), "\n";

// descending: swap the sides
usort($users, fn($a, $b) => $b['age'] <=> $a['age']);
echo $users[0]['name'], " is the oldest\n";

<?php
$codes = ['0', 'abc', '10'];
var_dump(in_array(0, $codes));          // loose: 0 == "0"
var_dump(in_array('1e1', $codes));      // loose: "1e1" == "10" as numbers
var_dump(in_array('1e1', $codes, true));

$roles = ['admin', 'editor', 'viewer'];
$pos = array_search('admin', $roles, true);
var_dump($pos);                          // 0 - found at the start
echo $pos !== false ? "admin found\n" : "no admin\n";

$config = ['debug' => null, 'port' => 8080];
var_dump(isset($config['debug']));               // null counts as "not set"
var_dump(array_key_exists('debug', $config));    // the key is there
var_dump(isset($config['port'], $config['debug']));

<?php
$letters = ['a', 'b', 'c', 'd', 'e'];

echo implode("", array_slice($letters, 1, 3)), "\n";    // b c d
echo implode("", array_slice($letters, -2)), "\n";      // last two

$removed = array_splice($letters, 1, 2, ['X', 'Y', 'Z']);
echo implode("", $letters), " (removed ", implode("", $removed), ")\n";

array_splice($letters, 1, 0, ['+']);                      // insert, remove nothing
echo implode("", $letters), "\n";

$a = [1, 2];
$b = [3, 4];
echo json_encode([...$a, ...$b, 5]), "\n";

$defaults = ['theme' => 'light', 'lang' => 'en'];
$chosen = ['lang' => 'hi'];
echo json_encode([...$defaults, ...$chosen]), "\n";     // later key wins
echo json_encode(array_merge($defaults, $chosen)), "\n";
echo json_encode($chosen + $defaults), "\n";            // left key wins
echo json_encode([1, 2] + [7, 8, 9]), "\n";             // + is by key!

<?php
[$first, $second] = ['gold', 'silver', 'bronze'];
echo "$first, $second\n";

[, , $third] = ['gold', 'silver', 'bronze'];         // skip positions
echo "$third\n";

$row = ['id' => 7, 'email' => '[email protected]', 'active' => true];
['id' => $id, 'email' => $email] = $row;             // by key, any order
echo "#$id $email\n";

[$x, [$y, $z]] = [1, [2, 3]];                          // nested
echo "$x $y $z\n";

$a = 'left';
$b = 'right';
[$a, $b] = [$b, $a];                                   // swap
echo "$a $b\n";

// functions "return several values" by returning an array
function minMax(array $nums): array
{
    return [min($nums), max($nums)];
}
[$lo, $hi] = minMax([4, 9, 1, 7]);
echo "min $lo, max $hi\n";

<?php
$orders = [
    ['id' => 101, 'customer' => 'Asha', 'items' => ['pen', 'ink']],
    ['id' => 102, 'customer' => 'Ravi', 'items' => ['notebook']],
    ['id' => 103, 'customer' => 'Asha', 'items' => []],
];

echo $orders[0]['items'][1], "\n";
echo implode(",", array_column($orders, 'id')), "\n";

$byId = array_column($orders, null, 'id');       // re-key rows by id
echo $byId[102]['customer'], "\n";

// group rows by a field
$byCustomer = [];
foreach ($orders as $order) {
    $byCustomer[$order['customer']][] = $order['id'];
}
echo json_encode($byCustomer), "\n";

$grid = [[1, 2, 3], [4, 5, 6]];
foreach ($grid as $r => $row) {
    foreach ($row as $c => $cell) {
        echo "[$r][$c]=$cell ";
    }
    echo "\n";
}

<?php
$a = [1, 2, 3];
$b = $a;          // shares memory until someone writes
$b[] = 4;         // now $b gets its own copy
echo json_encode($a), " ", json_encode($b), "\n";

function addItem(array $list): array
{
    $list[] = 'new';          // changes the function's copy
    return $list;
}
$items = ['old'];
$more = addItem($items);
echo json_encode($items), " ", json_encode($more), "\n";

$c = &$a;         // reference: two names, one array
$c[] = 99;
echo json_encode($a), "\n";