In today's lesson, we'll explore arrays in PHP, a flexible and integral data structure. PHP arrays are versatile and allow dynamic resizing, making them powerful for managing datasets where the size can change over time.

The strength of PHP arrays lies in their capability to dynamically allocate storage, providing efficient access and modification options. By the end of this lesson, you'll be able to create, manipulate, and understand the unique applications of arrays in PHP.

An array in PHP is a collection that can hold multiple items of different types and sizes and supports dynamic resizing. This flexibility allows arrays to grow as needed, unlike fixed-size data structures. PHP arrays handle their own memory allocation, making them highly adaptable.

Consider this PHP array declaration as an example:

php
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1<?php
2
3$my_array = ["apple", "banana", "cherry"];
4foreach ($my_array as $fruit) {
5    echo $fruit . " ";
6}
7// Output: apple banana cherry
8
9?>

In PHP, you can access array elements using the square brackets ([]) operator. Arrays can be modified by adding, removing, or changing elements.

The following is a simple example of inspecting and modifying arrays:

php
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1<?php
2
3$my_array = ["apple", "banana", "cherry"];
4
5// Accessing elements
6echo $my_array[1] . "\n"; // Output: banana
7echo $my_array[2] . "\n"; // Output: cherry
8
9// Modifying elements
10$my_array[1] = "blueberry"; // Modifying the second element
11echo $my_array[1] . "\n"; // Output: blueberry
12
13// Adding and removing elements
14$my_array[] = "durian"; // Adding a new element at the end
15unset($my_array[2]); // Removing the third element ("cherry")
16
17foreach ($my_array as $fruit) {
18    echo $fruit . " ";
19}
20// Output: apple blueberry durian
21
22?>

In this example:

• Accessing elements: $my_array[1] gets the second element ("banana"), and $my_array[2] gets the third element ("cherry").
• Modifying elements: $my_array[1] = "blueberry" changes the second element from "banana" to "blueberry".
• Adding and removing elements: $my_array[] = "durian" adds "durian" at the end. unset($my_array[2]) removes the third element ("cherry").

Arrays in PHP support several operations such as concatenation, insertion, and resizing.

php
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1<?php
2
3$arr1 = ["apple", "banana"];
4$arr2 = ["cherry", "durian"];
5
6// Concatenation: Merging $arr2 into $arr1
7$arr1 = array_merge($arr1, $arr2);
8
9foreach ($arr1 as $fruit) {
10    echo $fruit . " ";
11}
12// Output: apple banana cherry durian
13
14echo "\n";
15
16// Adding elements
17array_push($arr1, "elderberry", "elderberry"); // Add elements
18
19foreach ($arr1 as $fruit) {
20    echo $fruit . " ";
21}
22// Output: apple banana cherry durian elderberry elderberry
23
24echo "\n" . ($arr1[0] === "apple") . "\n"; // Output: 1 (true)
25
26?>

In the above example:

• array_merge($arr1, $arr2) merges arr2 into arr1.
• array_push($arr1, "elderberry", "elderberry") adds two "elderberry" elements to the end, expanding the array.
• $arr1[0] returns the first element of the array, which is "apple".

A PHP array can contain other arrays, resulting in nested arrays. These subarrays may not necessarily all have the same length. Here's an example of creating a nested array:

php
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1<?php
2
3$nested_array = [
4    ["apple", "banana"],
5    ["cherry", "durian", "orange"]
6];
7
8foreach ($nested_array as $sub_array) {
9    foreach ($sub_array as $fruit) {
10        echo $fruit . " ";
11    }
12    echo "\n";
13}
14// Output:
15// apple banana 
16// cherry durian orange
17
18?>

This example demonstrates how you can nest arrays and iterate through them using loops.

Great job! In this lesson, you've learned about PHP arrays and how to create, inspect, and manipulate them. We've covered some advanced concepts, like nested arrays, providing you with a strong foundation in array handling.

In upcoming practices, we'll provide exercises designed to reinforce these concepts. Remember, consistent practice is key to mastery. Keep experimenting with these examples by modifying and enhancing them. Let's continue diving deeper into PHP!