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    PHP Mastery Tutorial 0/120 lessons ~6 min read Lesson 21

    Arrays

    Arrays is a single PHP idea you'll use in almost every backend project. In this lesson you learn only arrays — not five topics at once. By the end you can write a small working…

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    Focus
    12 guided sections
    Practice signal
    Examples included
    Career prep
    Interview Q&A included

    Quick Introduction

    Arrays is a single PHP idea you'll use in almost every backend project.

    In this lesson you learn only arrays — not five topics at once. By the end you can write a small working example and explain it in an interview.

    We connect each lesson to our course projects: Login System, Blog CMS, REST API, Inventory, Employee Management, and E-Commerce Backend.

    Business Problem

    You're building the Employee Management. After a user signs in, you need arrays working correctly before storing data or showing a dashboard.

    Without understanding Arrays, the team ships bugs: wrong totals, broken sessions, or type errors that only appear in production. This lesson fixes that with one clear pattern you can copy into your project today.

    Core Concept

    • Arrays is one focused idea — learn it before mixing with other PHP topics.
    • Use it in PHP 8.3+ with declare(strict_types=1); at the top of every file.
    • Our course project (Employee Management) uses arrays in real handlers.
    • Run small scripts with php file.php after each change — don't just read.
    • Interviewers ask for a one-minute explanation plus a tiny code sample.

    Syntax

    Core syntax for Arrays. Every keyword below appears in production PHP — Laravel and Symfony use the same primitives under the hood.

    php
    declare(strict_types=1);

    Keywords: declare · strict_types · namespace

    Step-by-Step Example

    Run this script locally. Change one value, run again, and watch what changes.

    php
    <?php
    declare(strict_types=1);
    

    $prices = [19.99, 29.99, 9.99, 49.99];
    $labels = ['basic', 'pro', 'addon', 'enterprise'];
    

    // array_map, spread operator, destructuring, array_combine
    $withTax = array_map(fn(float $p) => round($p * 1.0825, 2), $prices);
    $merged  = [...$withTax, ...[99.99]];
    $catalog = array_combine($labels, array_slice($withTax, 0, count($labels)));
    

    [$first, $second, ...$rest] = $merged;
    $filtered = array_filter($rest, fn($v) => $v > 20.0);
    

    printf("First: %.2f | Second: %.2f | Rest count: %d\n", $first, $second, count($rest));
    print_r($catalog);
    print_r(array_values($filtered));

    Line by line

    1. — part of the arrays example; run the file to see the result.
    2. declare(strict_types=1); — turns on strict type checking for this file.
    3. $prices = [19.99, 29.99, 9.99, 49.99]; — part of the arrays example; run the file to see the result.
    4. $labels = ['basic', 'pro', 'addon', 'enterprise']; — part of the arrays example; run the file to see the result.
    5. $withTax = array_map(fn(float $p) => round($p * 1.0825, 2), $prices); — part of the arrays example; run the file to see the result.
    Authenticated

    Real-World Example

    In the Employee Management, arrays appears in a single request handler — not spread across ten files. Keep the example small, test it with php, then paste the pattern into your project branch.

    That is how Laracasts-style learning works: one concept, one file, one win per lesson.

    Best Practices

    • One concept per file while learning arrays.
    • Start from the course code sample, change one line, re-run.
    • Name variables and functions clearly — $loginCount beats $x.
    • Use PHP 8.3 on your machine; match the version in production later.
    • Write a one-sentence comment at the top: what this script proves about arrays.

    Common Mistakes

    • Trying to learn arrays together with three other topics in one sitting — split them like this course does.
    • Skipping declare(strict_types=1); and getting silent type coercion bugs.
    • Copying code without running it — always execute with php your-file.php.
    • Using outdated PHP 5 tutorials (mysql_*, short tags) instead of PHP 8.3 docs.
    • Not connecting arrays to the course project — practice inside Login, Blog, or Inventory code.

    Hands-on Exercise

    Task: Create a file arrays.php that demonstrates arrays for the Employee Management.

    Challenge: Add one edge case (empty input, zero, or invalid type) and print a friendly error message.

    php
    <?php
    declare(strict_types=1);
    

    // TODO: Arrays exercise for Employee Management

    Summary

    • Arrays is one concept — master it before combining with the next lesson.
    • Always use strict_types while learning PHP 8.3+.
    • Practice inside the Employee Management codebase as you progress.
    • Run code with php after every edit.
    • You can explain this topic in under two minutes with the sample script.
    • Next lesson builds on this — don't skip the exercise.

    Key Takeaways

    • You know what Arrays is and when to use it.
    • You can read and write the syntax from this lesson.
    • You ran the example and changed it successfully.
    • You can spot the five common mistakes listed above.
    • You answered at least three interview questions out loud.

    Interview Questions

    Q1BeginnerWhat is Arrays in PHP?
    Arrays lets you talk to the database in PHP. In our Employee Management, it appears in small, testable scripts before we move code into classes.
    Q2BeginnerWhy use Arrays instead of a shortcut?
    Shortcuts hide bugs. Arrays makes behavior explicit so teammates and PHPStan can understand your code.
    Q3BeginnerShow a minimal Arrays example.
    Open this lesson's sample file, run it with php, and explain each line in plain English — that is enough for a junior interview.
    Q4BeginnerCommon beginner mistake with arrays?
    Mixing multiple new concepts in one file. Learn Arrays alone first, then combine in the course project.
    Q5BeginnerHow do you test arrays locally?
    Save a .php file, run php file.php, and compare output to what you expected. Add one PHPUnit test when you move code into a class.
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