How do you start a PHP script?

1. The Basic Syntax: The PHP Tags

A PHP script starts with the <?php opening tag and ends with the ?> closing tag. Any code between these tags is interpreted as PHP.

Basic Structure:

<?php
// This is where your PHP code goes
?>

<?php: This is the standard and recommended way to start a PHP script. It's guaranteed to work on every server configuration.
?>: This is the closing tag. If a file contains only PHP code, it is actually recommended to omit the closing tag to avoid unwanted whitespace or newline characters causing issues.

2. Your First Simple Script: "Hello, World!"

Let's create a basic script that outputs text.

Example: hello.php

<?php
echo "Hello, World!";
?>

Explanation:

echo is a language construct used to output (print) one or more strings.
The line ends with a semicolon (;). In PHP, almost every line of code that is a statement must end with a semicolon.

3. How to Run a PHP Script (The Crucial Part)

Unlike HTML files, which you can simply open in a browser, PHP files need to be executed by a PHP interpreter on a web server. You cannot run them by double-clicking the file.

You have three main options to run a PHP script:

Option A: Using a Local Development Server (Most Common for Learning)

This is the best way to learn and test. You install a software stack on your own computer that includes a web server (like Apache or Nginx) and the PHP interpreter.

Install a Package:
- Windows: XAMPP, WampServer, or Laragon.
- macOS: XAMPP, MAMP, or use the built-in PHP with Homebrew.
- Linux: Use your package manager (e.g., sudo apt install apache2 php mysql-server).
Start the Servers: Open the control panel (e.g., XAMPP) and start the "Apache" web server.
Place Your File: Put your PHP file (e.g., hello.php) inside the "web root" directory. This is typically:
- XAMPP: C:\xampp\htdocs\ (Windows) or /Applications/XAMPP/htdocs/ (macOS)
- WampServer: C:\wamp64\www\
Run in Browser: Open your web browser and go to: http://localhost/hello.php

The browser will display: Hello, World!

Option B: Using PHP's Built-in Development Server (Quick & Easy)

For simple testing, PHP has a built-in web server. This is not suitable for production but is perfect for quick experiments.

Open a Terminal or Command Prompt.
Navigate to the directory where your hello.php file is located.
```
cd /path/to/your/php/script
```
Start the server on a specific port (e.g., 8000):
```
php -S localhost:8000
```
Run in Browser: Go to http://localhost:8000/hello.php

Option C: On a Live Web Hosting Server (For a Real Website)

When you want to put your website online, you upload your .php files to a web hosting provider that supports PHP.

Upload hello.php to your public directory (often called public_html or htdocs) using an FTP client or file manager.
Access it via your domain name: http://yourwebsite.com/hello.php

4. Key Ways to "Start" or Trigger Output Within a Script

Once your script is running, you need ways to produce output and execute logic.

Method	Description	Example
`echo` / `print`	Outputs strings or variables. `echo` can take multiple parameters; `print` can only take one.	`echo "Hello, ", $name;`
HTML outside PHP tags	You can write HTML directly, and use PHP tags for the dynamic parts.	(See example below)
Variables	Start with a `$` sign.	`$message = "Welcome!";`
Conditionals (`if`)	Execute code based on conditions.	(See example below)

Practical Example: Mixing HTML and PHP

A PHP file can be mostly HTML, with PHP snippets inside it to generate dynamic content. This is very common.

File: welcome.php

<!DOCTYPE html>
<html>
<head>
    <title>My PHP Page</title>
</head>
<body>
    <h1>Welcome to my Site</h1>

    <!-- This is pure HTML -->
    <p>This is a static paragraph.</p>

    <?php
    // This is a PHP code block
    $userName = "Alice";
    $hour = date('H'); // Gets the current hour (0-23)

    // Use an if/else statement to change the message
    if ($hour < 12) {
        $greeting = "Good morning";
    } else {
        $greeting = "Good afternoon";
    }

    // Output the dynamic greeting
    echo "<p>$greeting, $userName!</p>";
    ?>

    <p>This is more static HTML.</p>

</body>
</html>

Expected Output in Browser:

Welcome to my Site

This is a static paragraph.

Good afternoon, Alice! (This will change based on the time of day)

This is more static HTML.

Summary: How to Start

Write your code inside <?php ... ?> tags.
Save the file with a .php extension.
Run it on a server (local like XAMPP, the built-in PHP server, or a live web host).
View the output in your web browser by visiting the script's URL.

The most important takeaway is that PHP is a server-side technology. You must always access your .php files through a URL (http://...) that is handled by a web server with PHP enabled, not by opening the file directly from your file system (file://...).

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