Arrays & Data Collections — PHP Course

What you'll learn

PHP arrays are ordered maps: one type can represent a list, a key-value record, or nested data. You'll learn to shape arrays deliberately and transform them without losing clarity.

Create indexed and associative arrays
Safely read, add, update, and remove values
Model nested data
Map, filter, and reduce collections
Sort, destructure, and spread values

Lists and records

Integer keys naturally model ordered lists. String keys model named fields. Both use the short [...] syntax.

arrays.php

<?php

$topics = ['syntax', 'arrays', 'functions'];

$student = [
    'name' => 'Nour',
    'level' => 'beginner',
    'completed' => 3,
];

echo $topics[1] . PHP_EOL;
echo $student['name'];

Key idea

An array's shape is part of your program's design. Keep the same keys and value types for every record in a collection; inconsistent shapes create defensive code everywhere.

Read and change values safely

update.php

<?php

$cart = ['book', 'pen'];
$cart[] = 'notebook';       // append
$cart[1] = 'blue pen';      // update
unset($cart[0]);             // remove; remaining keys are not reset

$profile = ['name' => 'Nour'];
$profile['city'] = 'Beirut';

echo count($cart) . PHP_EOL;
echo $profile['city'];

Question	Tool
Does this key exist, even if its value is null?	`array_key_exists($key, $array)`
Does this key exist and contain a non-null value?	`isset($array[$key])`
Does this list contain a value?	`in_array($value, $array, true)`
How many elements are present?	`count($array)`

Tip

Pass true as the third argument to in_array() for strict comparison. It avoids treating values such as 0 and "0" as interchangeable.

Nested and multidimensional data

students.php

<?php

$students = [
    ['name' => 'Nour', 'scores' => [82, 91]],
    ['name' => 'Ziad', 'scores' => [76, 88]],
];

echo $students[0]['name'] . ': ' . $students[0]['scores'][1];

Nested arrays mirror JSON-like data well. When a shape carries important business rules or behavior, a class will eventually communicate the model better; that arrives in Phase 3.

Map, filter, and reduce

array_map() transforms every item, array_filter() keeps matching items, and array_reduce() combines a collection into one result.

prices.php

<?php

$prices = [12.50, 8.00, 22.40, 5.00];

$salePrices = array_map(
    fn (float $price): float => $price * 0.9,
    $prices
);

$overTen = array_filter(
    $salePrices,
    fn (float $price): bool => $price > 10
);

$total = array_reduce($overTen, fn ($sum, $price) => $sum + $price, 0.0);
echo number_format($total, 2);

Sort, destructure, and spread

organize.php

<?php

$scores = [72, 95, 81];
rsort($scores);

[$highest, $second] = $scores;
$allScores = [...$scores, 68, 90];

echo "{$highest}, {$second}" . PHP_EOL;
echo implode(', ', $allScores);

Sorting can change keys

Functions such as sort() and rsort() reindex numeric keys. Associative sorting functions such as asort() preserve key associations. Choose by the data contract you need.

Recap & quick check

Key takeaways

PHP arrays are ordered maps that can represent lists or named records.
Use isset, array_key_exists, and strict in_array for different existence questions.
Nested arrays model structured data, but important domain behavior may deserve a class.
Map transforms, filter selects, and reduce combines.
Know whether a sorting function preserves keys before using it.

Quick check

1. Which syntax appends an item to a list?

2. Which check distinguishes an existing null key from a missing key?

3. Which operation keeps only matching elements?