อาร์เรย์แบบดัชนีและแบบเชื่อมโยง

<?php
$colors = ['red', 'green', 'blue'];    // short syntax
$nums   = array(10, 20, 30);            // long syntax

echo $colors[0]; // red
echo $nums[2];   // 30
echo count($colors); // 3

<?php
$items = ['a', 'b', 'c'];
$items[] = 'd';      // append
$items[] = 'e';

unset($items[1]);    // remove 'b'

print_r($items);
// [0=>'a', 2=>'c', 3=>'d', 4=>'e'] — index gap!

<?php
$person = [
    'name'  => 'Alice',
    'age'   => 30,
    'email' => 'alice@example.com',
];

echo $person['name'];   // Alice
$person['city'] = 'London';  // add new key
unset($person['email']);      // remove key

<?php
$config = ['debug' => false, 'version' => '2.0'];

var_dump(array_key_exists('debug', $config));  // true
var_dump(isset($config['debug']));             // false! debug=false, not NULL
var_dump(in_array('2.0', $config));            // true

<?php
$data = ['key' => null];

var_dump(isset($data['key']));              // false
var_dump(array_key_exists('key', $data));  // true

<?php
$point = [10, 20, 30];
[$x, $y, $z] = $point;
echo "x=$x y=$y z=$z"; // x=10 y=20 z=30

// Skip elements
[, $second] = [1, 2, 3];
echo $second; // 2

<?php
$a = ['x' => 1, 'y' => 2];
$b = ['y' => 99, 'z' => 3];

$merged = array_merge($a, $b);
print_r($merged); // x=>1, y=>99 (b overwrites), z=>3

$union = $a + $b;
print_r($union);  // x=>1, y=>2 (a wins), z=>3

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

$slice = array_slice($letters, 1, 3);
print_r($slice); // ['b', 'c', 'd']

$last2 = array_slice($letters, -2);
print_r($last2); // ['d', 'e']

<?php
$stack = [];
array_push($stack, 'a', 'b');
$top = array_pop($stack);  // 'b' — LIFO

$queue = ['first', 'second'];
array_push($queue, 'third');
$front = array_shift($queue);  // 'first' — FIFO

array_unshift($queue, 'zero'); // prepend

<?php
$name = 'Alice';
$age  = 30;

$data = compact('name', 'age');
// ['name' => 'Alice', 'age' => 30]

extract(['city' => 'London', 'country' => 'UK']);
echo $city;    // London
echo $country; // UK