PHP Intro

PHP Intro: Server-Side Web Scripting with PHP 8

PHP (Hypertext Preprocessor) is an open-source, server-side scripting language built for web development. When a browser requests a PHP page, the web server runs the PHP script first and sends only plain HTML or JSON back to the user.

How PHP Runs on the Server

Because PHP executes on your backend server, visitors never see your source code, database passwords, or internal business rules.

flowchart LR
    A["Browser Request"] --> B["Web Server (Nginx / Apache)"]
    B --> C["PHP 8 Runtime"]
    C --> D["MySQL Database"]
    D --> C
    C --> E["HTML or JSON Response"]
    E --> A

Modern PHP 8 powers small business sites, custom REST APIs, and large platforms like WordPress and Laravel. It runs on Linux, macOS, and Windows servers without changing your application code.

Your First Dynamic PHP Page

You can mix PHP logic with HTML templates by wrapping server instructions inside <?php ... ?> tags. Always escape dynamic strings with htmlspecialchars() so user input cannot inject unsafe scripts into the page.

<?php
declare(strict_types=1);

$serverTime = date('Y-m-d H:i:s');
$userRole = 'Editor';
$activeModules = ['User Accounts', 'Invoice Generator', 'Email Queue'];
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>PHP Server Status</title>
</head>
<body>
    <h2>PHP Server Information</h2>
    <p>Server Time: <strong><?= htmlspecialchars($serverTime) ?></strong></p>
    <p>Current Role: <span><?= htmlspecialchars($userRole) ?></span></p>

    <h3>Enabled Modules</h3>
    <ul>
        <?php foreach ($activeModules as $module): ?>
            <li><?= htmlspecialchars($module) ?></li>
        <?php endforeach; ?>
    </ul>
</body>
</html>

Common Mistakes to Avoid

• Opening .php files directly from your file explorer: Browsers cannot run PHP locally via file://. Always serve files through a web server or php -S localhost:8000.
• Echoing raw user input: Printing $_GET or database strings without htmlspecialchars() creates Cross-Site Scripting (XSS) vulnerabilities.
• Mixing SQL queries inside HTML templates: Fetch and process data in dedicated PHP functions before rendering your view markup.

Frequently Asked Questions

Can browsers execute PHP code directly?

No. Browsers only understand HTML, CSS, and JavaScript. The web server executes PHP first and returns the rendered output to the browser.

Is PHP still used for new projects?

Yes. PHP 8 offers typed properties, JIT compilation, and mature frameworks like Laravel and Symfony that power millions of modern production APIs and websites.

What file extension does a PHP script require?

Save PHP scripts with the .php extension so the web server knows to pass the file to the PHP interpreter instead of serving it as plain text.