Arrays in PHP – a complete guide

Arrays in PHP are one of the most important data structures. They allow you to store multiple values in a single variable. In this chapter, you will learn how to declare arrays, perform operations, iterate, sort, and use PHP’s rich set of built-in functions.

Declaring arrays

<?php
// Indexed array
$fruits = ["apple", "banana", "orange"];

// Associative array
$user = [
    "name" => "John",
    "age" => 25,
    "active" => true
];

// Multidimensional array
$matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];

Accessing elements

echo $fruits[0]; // apple
echo $user["name"]; // John

Basic operations

• count($array) – number of elements
• array_push($array, $value) – add element
• array_pop($array) – remove the last element
• unset($array[$index]) – remove a selected element
• in_array($value, $array) – check if a value exists

Iterating over arrays

foreach ($fruits as $fruit) {
    echo $fruit . "\n";
}

foreach ($user as $key => $value) {
    echo "$key: $value\n";
}

Sorting arrays

• sort($array) – sort ascending
• rsort($array) – sort descending
• asort($array) – sort associative array by values
• ksort($array) – sort associative array by keys

$numbers = [3, 1, 4, 2];
sort($numbers);
print_r($numbers); // [1, 2, 3, 4]

Useful array functions

• array_merge() – merging arrays
• array_keys() and array_values()
• array_map() – apply a function to each element
• array_filter() – filter an array
• array_reduce() – reduce to a single value

$nums = [1, 2, 3, 4];
$sum = array_reduce($nums, fn($carry, $item) => $carry + $item, 0);
echo $sum; // 10

Best practices

1. Use associative arrays instead of multiple variables with similar meaning.
2. When iterating over large arrays, prefer foreach – it’s clear and safe.
3. For filtering and mapping, use built-in functions instead of writing loops manually.