PHP — Sorting Arrays

Creating arrays

PHP offers two syntaxes:

<?php
// array() function
$fruits = array("Apple", "Banana", "Cherry");

// Short syntax (preferred)
$colors = ["Red", "Green", "Blue"];

// Empty array
$empty = [];

// With range
$numbers = range(1, 10); // [1, 2, 3, ..., 10]
?>

Indexed arrays

Numerically indexed, starting from 0:

<?php
$fruits = ["Apple", "Banana", "Cherry"];

echo $fruits[0];    // Apple
echo $fruits[1];    // Banana
echo count($fruits); // 3

// Add to end
$fruits[] = "Date"; // Append

// Add at index
$fruits[10] = "Fig"; // Sparse array — indices 3-9 are empty
?>

Associative arrays

String keys for labeled data:

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

echo $person["name"];   // Alice
echo $person["age"];    // 30

// Add new key-value pair
$person["phone"] = "555-1234";
?>

Multidimensional arrays

Arrays within arrays:

<?php
$matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];

echo $matrix[1][2]; // 6

$users = [
    ["name" => "Alice", "age" => 30],
    ["name" => "Bob", "age" => 25],
    ["name" => "Charlie", "age" => 35]
];

echo $users[0]["name"]; // Alice
?>

Common array functions

<?php
$fruits = ["Apple", "Banana", "Cherry"];

// Size and presence
echo count($fruits);             // 3
echo in_array("Banana", $fruits); // true

// Search
$key = array_search("Cherry", $fruits); // 2
echo array_key_exists("name", $person); // true

// Add and remove
$fruits[] = "Date";              // Append to end
array_push($fruits, "Elder");    // Push to end
$last = array_pop($fruits);      // Remove from end
$first = array_shift($fruits);   // Remove from beginning
array_unshift($fruits, "Fig");   // Add to beginning

// Sort
sort($fruits);                   // Sort ascending
rsort($fruits);                  // Sort descending
asort($fruits);                  // Sort by value, keep keys
ksort($fruits);                  // Sort by key
usort($fruits, fn($a, $b) => strlen($a) <=> strlen($b)); // Custom sort
?>

Array transformation

<?php
$numbers = [1, 2, 3, 4, 5];

// Map: transform each element
$doubled = array_map(fn($n) => $n * 2, $numbers);
print_r($doubled); // [2, 4, 6, 8, 10]

// Filter: keep elements matching a condition
$evens = array_filter($numbers, fn($n) => $n % 2 == 0);
print_r($evens); // [2, 4]

// Reduce: accumulate into a single value
$sum = array_reduce($numbers, fn($carry, $n) => $carry + $n, 0);
echo $sum; // 15

// Flip keys and values
$flipped = array_flip(["a" => 1, "b" => 2]);
print_r($flipped); // [1 => "a", 2 => "b"]
?>

Slicing and combining

<?php
$numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

// Slice
$slice = array_slice($numbers, 2, 3); // [2, 3, 4]
$lastThree = array_slice($numbers, -3); // [7, 8, 9]

// Merge
$a = [1, 2, 3];
$b = [4, 5, 6];
$merged = array_merge($a, $b); // [1, 2, 3, 4, 5, 6]

// Combine keys and values
$keys = ["name", "age", "email"];
$values = ["Alice", 30, "alice@example.com"];
$person = array_combine($keys, $values);
print_r($person);
// [name => Alice, age => 30, email => alice@example.com]

// Fill
$zeros = array_fill(0, 5, 0); // [0, 0, 0, 0, 0]

// Chunk
$chunked = array_chunk($numbers, 3);
print_r($chunked);
// [[0,1,2], [3,4,5], [6,7,8], [9]]
?>

Destructuring arrays

<?php
// List syntax
$colors = ["Red", "Green", "Blue"];
list($first, $second, $third) = $colors;
echo "$first, $second, $third"; // Red, Green, Blue

// Short syntax (PHP 7.1+)
[$a, $b, $c] = [1, 2, 3];

// Skip elements
[, $second, $third] = ["a", "b", "c"];
echo "$second, $third"; // b, c

// Associative destructuring
["name" => $name, "age" => $age] = ["name" => "Alice", "age" => 30];
echo "$name is $age"; // Alice is 30
?>

Spread operator

<?php
// Unpack arrays
$a = [1, 2];
$b = [3, 4];
$combined = [...$a, ...$b]; // [1, 2, 3, 4]

// Function arguments
$numbers = [3, 1, 4, 1, 5];
$max = max(...$numbers); // 5
$sum = array_sum($numbers); // 14

// Copy
$copy = [...$numbers];
?>

Mini Practice

Write PHP code that:

1. Creates an associative array of 5 products with prices
2. Filters products that cost more than $10
3. Uses array_map to apply a 10% discount to all prices
4. Destructures the first two elements of an indexed array

Up Next

In the next lesson, you'll learn about Functions — defining, calling, and working with function parameters.