Arrays in PHP

A PHP array is an ordered map that associates keys with values and can work as a list or dictionary.

In real web development, you almost never work with isolated data. You work with lists of products, collections of users, or rows from a database. For all of this, we use Arrays.

The short syntax [] is the standard way to declare arrays. The array() syntax is still valid, but it’s less common in modern code.

Indexed arrays (lists)

These are the classic arrays. A list of elements where each one has a numeric position (index), always starting at 0.

// Definition
$technologies = ['PHP', 'Laravel', 'Docker', 'React'];

// Access
echo $technologies[0]; // Output: PHP
echo $technologies[2]; // Output: Docker

// Add an element to the end
$technologies[] = 'Linux';

PHP automatically assigns the numbers:

• 0 => ‘PHP’
• 1 => ‘Laravel’
• …

When to use them? When order matters and the elements are of the same type (e.g., a list of prices, a list of names).

Associative arrays (dictionaries / maps)

This is where PHP shines. Instead of using automatic numbers to access data, you define Keys with meaningful names.

It’s the equivalent of a JSON Object or a Python Dictionary.

$product = [
    'name' => '4K Monitor',
    'price' => 299.99,
    'stock'  => true,
    'brand'  => 'Dell'
];

// Access (much more readable)
echo "The product {$product['name']} costs {$product['price']}€";

Notice the arrow =>. It means “This key points to this value”.

When to use them? When you want to describe an entity with properties (a user, a product, a configuration).

Multidimensional arrays (inception)

An array can contain… other arrays! This allows handling more complex data structures.

Imagine a list of users (Indexed) where each user has their data (Associative).

$users = [
    [
        'name' => 'Luis',
        'role'    => 'Admin'
    ],
    [
        'name' => 'Ana',
        'role'    => 'Editor'
    ]
];

// Access the name of the second user
echo $users[1]['name']; // Output: Ana

Modern manipulation (spread operator ...)

Since PHP 7.4 we can unpack arrays with numeric keys using ...; PHP 8.1 added support for string keys. It’s a convenient alternative to array_merge in many cases.

$fruits = ['Apple', 'Pear'];
$vegetables = ['Lettuce', 'Tomato'];

// Merge into a new one
$basket = [...$fruits, ...$vegetables, 'Bread'];

// Result: ['Apple', 'Pear', 'Lettuce', 'Tomato', 'Bread']

It’s fast, visual, and very powerful.

echo "<pre>";
var_dump($users);
echo "</pre>";