Arrays & Collections 📦

Master PHP's most powerful data structure — indexed arrays, associative arrays, multidimensional arrays, and 30+ built-in array functions.

What You'll Learn in This Lesson

• Indexed arrays for ordered lists of values
• Associative arrays with string keys (key => value)
• Multidimensional arrays for complex data structures
• Sorting, searching, filtering, and transforming arrays
• array_map, array_filter, array_reduce for functional programming

Note: PHP runs on a server. Our examples simulate PHP logic using JavaScript. To run real PHP, install PHP.

🎯 Real-World Analogy: An indexed array is like a numbered shopping list — item #1, #2, #3. An associative array is like a contact card — "name" → "Alice", "email" → "alice@example.com". A multidimensional array is like a filing cabinet with labelled drawers, each containing folders with documents inside.

1️⃣ Three Types of PHP Arrays

Type	Syntax	Use Case
Indexed	["a", "b", "c"]	Ordered lists
Associative	["name" => "Alice"]	Key-value data
Multidimensional	[["a", 1], ["b", 2]]	Tables, nested data

Try It: Array Types

Create indexed, associative, and multidimensional arrays and access their elements

Try it Yourself »

JavaScript

// PHP Arrays & Collections (simulated in JavaScript)
console.log("=== Indexed Arrays ===");
console.log();

// PHP: $fruits = ["Apple", "Banana", "Cherry", "Date"];
let fruits = ["Apple", "Banana", "Cherry", "Date"];

console.log("Fruits array: [" + fruits.join(", ") + "]");
console.log("First:  $fruits[0] = " + fruits[0]);
console.log("Last:   $fruits[3] = " + fruits[3]);
console.log("Count:  count($fruits) = " + fruits.length);

console.log();

// Adding elements
fruits.push("Elderberry");  /
...

Try It: Array Functions

Sort, search, filter, map, reduce, merge, and slice arrays

Try it Yourself »

JavaScript

// PHP Array Functions (simulated in JavaScript)
console.log("=== Sorting Arrays ===");
console.log();

let numbers = [5, 2, 8, 1, 9, 3, 7];
console.log("Original: [" + numbers.join(", ") + "]");

// sort() — sorts ascending
let sorted = [...numbers].sort((a, b) => a - b);
console.log("sort():   [" + sorted.join(", ") + "]");

// rsort() — sorts descending
let rsorted = [...numbers].sort((a, b) => b - a);
console.log("rsort():  [" + rsorted.join(", ") + "]");

console.log();
console.log("=== Sea
...

⚠️ Common Mistakes

⚠️

Confusing indexed and associative — PHP arrays can mix both. [0 => "a", "name" => "b"] is valid but confusing. Pick one style per array.

⚠️

Using sort() on associative arrays — sort() re-indexes keys! Use asort() to preserve key-value associations.

⚠️

Modifying arrays during foreach — can cause unexpected behaviour. Build a new array with array_map() or array_filter() instead.

💡

Pro Tip: Use array_map(), array_filter(), and array_reduce() for clean, functional-style code. They're faster and safer than manual loops.

📋 Quick Reference — PHP Arrays

Function	Purpose	Returns
count()	Array length	int
in_array()	Check if value exists	bool
array_map()	Transform each element	array
array_filter()	Keep matching elements	array
array_merge()	Combine arrays	array
sort() / asort()	Sort values	void (modifies)

🎉 Lesson Complete!

You've mastered PHP arrays! Next, learn how to read and write files on the server.