PHP Indexed Arrays: Numeric Indexing, Operations & Sorting

An Indexed Array (also known as a numeric array) is an ordered collection where each value is automatically assigned a numeric index starting at 0. Indexed arrays are the standard choice whenever you need to maintain an ordered list of items, such as a list of blog post titles, product IDs, or student examination scores.

Creating Indexed Arrays

You can create an indexed array automatically using sequential assignment or by explicitly assigning specific indices:

<?php
    // Auto-indexed assignment (Index 0, 1, 2)
    $cars = ["Volvo", "BMW", "Toyota"];

    // Explicit manual indexing
    $colors[0] = "Red";
    $colors[1] = "Green";
    $colors[2] = "Blue";

    // Accessing elements via numeric index:
    echo "First car: " . $cars[0] . "<br>"; // Volvo
    echo "Second car: " . $cars[1] . "<br>"; // BMW
?>

Adding & Modifying Elements

You can add new items to the end of an indexed array using empty square brackets [] or replace an existing element by specifying its index:

<?php
    $cities = ["Delhi", "Mumbai", "Kolkata"];

    // Appending an item to the end
    $cities[] = "Chennai";     // Automatically assigned index 3
    array_push($cities, "Pune"); // Appended at index 4

    // Modifying an existing item
    $cities[0] = "New Delhi";  // Replaces "Delhi" at index 0

    print_r($cities);
?>

Traversing Indexed Arrays: for vs foreach

<?php
    $scores = [78, 85, 92, 64, 88];

    // Method 1: Using for loop with count()
    $total = count($scores);
    for ($i = 0; $i < $total; $i++) {
        echo "Score at index [$i] = " . $scores[$i] . "<br>";
    }

    // Method 2: Using foreach loop (Cleaner & Safer)
    foreach ($scores as $index => $score) {
        echo "Student #$index earned: $score%<br>";
    }
?>

Sorting Indexed Arrays: sort() and rsort()

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