Introduction

“Hello World” is the classic first program in almost every programming language. In PHP, it helps you understand:

what a .php file is,
how to run code on an HTTP server,
how to use output instructions (functions/commands for displaying text) — in PHP this is mainly echo.

This lesson is a simple but thorough guide that takes you from environment setup, through creating a PHP file, to running your first “Hello World” program in both the browser and the terminal. You’ll also find code examples, best practices, and common beginner mistakes.

Basics: What Is PHP and How Does Output Work?

PHP is a server-side scripting language. This means that PHP code is executed on the server, and the result (usually HTML) is sent to the browser.
To see PHP output in the browser, you need an HTTP server with PHP enabled — e.g., XAMPP, WAMP, MAMP, Laragon, or PHP’s built-in server.
To display text, we use echo (or less commonly print). Echo sends text to the output stream, which the server then delivers to the browser.

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Preparing the Environment and PHP File Location

Option A: Package with Server (Easiest for Beginners)

Install:

* Windows: XAMPP, WAMP, Laragon * macOS: MAMP, XAMPP * Linux: packages apache2 + php (or use the built-in PHP server — see below)

Start the server (Apache) from the package control panel.
Where to put your .php file:

* XAMPP (Windows/macOS): htdocs folder

* Windows typical: C:\xampp\htdocs\
* macOS typical: /Applications/XAMPP/htdocs/
* MAMP: Applications/MAMP/htdocs/

Open in browser: http://localhost/filename.php or http://localhost/folder/index.php.

Option B: PHP Built-in Server (No Apache Installation)

Install PHP (check in terminal: php -v).
In your chosen project folder, run:

* php -S localhost:8000

Open in browser: http://localhost:8000

This is a great option for learning and small examples.

Editor and File Encoding

Use a simple editor: VS Code, Sublime Text, Notepad++, PHPStorm (optional).
Save files in UTF-8 without BOM, with the .php extension (e.g., index.php).

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Your First PHP File: Hello World

Step by Step (XAMPP/MAMP)

Open the server folder (e.g., htdocs).
Create a project folder, e.g., hello.
Inside it, create a file index.php.
Paste the code:

<?php
// This is a comment in PHP. The line below will display text in the browser.
echo "Hello, World!";

Open the browser and type:

* XAMPP/MAMP: http://localhost/hello/ or http://localhost/hello/index.php

You should see: Hello, World!

Step by Step (Built-in PHP Server)

Choose any folder (e.g., C:\projects\hello or ~/projects/hello).
Create an index.php file inside it with the code above.
In the terminal, run in that folder:

* php -S localhost:8000

Open in browser: http://localhost:8000

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How Echo Works and Displaying Output

Basics of echo

echo is a language construct (not a function), it can take one or more arguments.
Common usage:

<?php
echo "Hello, World!";         // Displays simple text
echo "<br>";                  // HTML line break (in browser)
echo "This is the second line."; // Another text

Echo with or without Parentheses

Both forms are valid:

<?php
echo "Hi";      // without parentheses
echo("Hi");     // with parentheses (less common, but works)

Concatenating Strings

<?php
$name = "Anna";
echo "Hello, " . $name . "!"; // dot operator concatenates strings

Double vs Single Quotes

In double quotes, variables are interpolated:

<?php
$name = "Jake";
echo "Hi, $name!"; // Hi, Jake!

In single quotes, variables are not interpolated:

<?php
$name = "Jake";
echo 'Hi, $name!'; // Displays literally: Hi, $name!

Special Characters and New Lines

In HTML, the simplest new line is the   tag.
In terminal/CLI, use \n:

<?php
echo "Line 1\n";
echo "Line 2\n";

Short Echo Tag:

Shortcut for echo (always available since PHP 5.4+):

<?php
$name = "Ola";
?>
<p>Hello, <?= htmlspecialchars($name) ?>!</p>

This is convenient in HTML files.

PHP Code Examples (with Comments)

1) Minimal Hello World

<?php
// Simplest possible example:
echo "Hello, World!";

2) Hello World with HTML

<?php
// PHP can coexist with HTML in one file:
$title = "First PHP Page";
?>
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title><?= htmlspecialchars($title) ?></title>
</head>
<body>
  <h1><?php echo "Hello, World!"; ?></h1>
  <p>This is my first PHP code.</p>
</body>
</html>

3) Multiple echo and Formatting

<?php
echo "<h2>Hello, World!</h2>";
echo "<p>This is a paragraph.</p>";
echo "<ul>";
echo "<li>Item 1</li>";
echo "<li>Item 2</li>";
echo "</ul>";

4) Echo with Variables

<?php
$name = "Barbara";
$year = 2025;
echo "Hello, $name! The year is $year.";

5) Echo in CLI (Terminal)

Save as hello.php:

<?php
echo "Hello, World!\n"; // \n creates a new line in console

Run:

php hello.php

6) Avoiding Quote Conflicts

<?php
// When you need quotes in text:
echo "This is \"a quote\" inside text.";
echo 'This is "a quote" inside text.'; // alternative: use single quotes

Best Practices and Common Mistakes

Best Practices

Always use full PHP opening tag: \ … (don’t use <?).

Save files as UTF-8 without BOM (avoids invisible characters at file start).

In pure PHP files, don’t close the ?> tag at the end — avoids accidental spaces and header issues.

For mixing HTML and PHP, use the short echo <?= ... ?> — makes templates cleaner.

When displaying user data, always use htmlspecialchars() for security (prevents XSS):

<?php
$nick = $_GET['nick'] ?? 'Guest';
echo "Hello, " . htmlspecialchars($nick, ENT_QUOTES, 'UTF-8');

In browser, use   for new lines; in CLI, use \n.

File names: no spaces or special characters, use hello.php, index.php.

Common Beginner Mistakes

Wrong way of opening files in browser:

* Mistake: opening via file:///C:/.../index.php (skips server, PHP won’t run). * Correct: http://localhost/...

Missing semicolon at the end of a statement:

echo "Hello" // missing ; causes syntax error

Saving file as .txt instead of .php.

Incorrect quotes or mixing ' and ":

echo "This is 'ok'"; // fine echo "This is "error""; // error

Spaces/characters before <?php (especially with BOM files) — may cause header warnings or break output.

Using short_open_tag (<?) — may not work on many servers. Stick to <?php and <?=.

Expecting \n to be visible in the browser — in HTML you need   or CSS styles.

Placing files outside the server directory (e.g., outside htdocs in XAMPP) and trying to access via http://localhost/... — won’t work.

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Summary

PHP is a server-side language for building web pages and applications.

First step is setting up the environment (XAMPP/MAMP or PHP built-in server).

Save code in .php files and run via http://localhost or in terminal (php file.php).

Use echo for output, remembering semicolons, quotes, and new lines (HTML:  , CLI: \n).

Stick to best practices: <?php, <?= ?>, UTF-8 without BOM, htmlspecialchars for user data.

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Mini Quiz – Test Yourself!

What’s the difference between opening index.php with file:// and http://localhost/?

Which PHP statement displays the text “Hello, World!”?

What does <?= $variable ?> do and when is it useful?

How do you make a new line in:

* a) browser, * b) terminal/CLI?

Why should you save files in UTF-8 without BOM?

What happens if you forget a semicolon after echo "text"?

What’s the difference between single and double quotes in PHP regarding variables?

How do you safely display user-provided data?

Answers

file:// doesn’t run PHP (browser shows raw code or nothing). http://localhost/ goes through the server with PHP interpreter.

echo "Hello, World!";

It’s shorthand for echo; useful in HTML templates for clean output.

a) use  ; b) use \n.

Avoids invisible characters at file start and header/output issues.

Syntax error (Parse error).

In double quotes variables are interpolated, in single quotes they are shown literally.

Use htmlspecialchars($data, ENT_QUOTES, 'UTF-8') before echo.

Good luck with your PHP learning journey!