PHP runs on the server side. When the user requests the page, the server executes the code through the PHP engine and returns HTML to ensure that the PHP code is not seen by the front end. 1. Request processing: Use $_GET, $_POST, $_SESSION, $_SERVER to obtain data, always verify and filter inputs to ensure security. 2. Separation of logic and display: Separate data processing from HTML output, use PHP files to process logic, and template files are responsible for displaying, improving maintainability. 3. Automatic loading and file structure: Configure PSR-4 automatic loading through Composer, such as "App\": "src/", to automatically introduce class files. The recommended project structure is: public/storage entry index.php, src/storage class, config/storage configuration, views/storage templates, composer.json management dependencies. Beginner steps: Install the PHP environment, configure Composer, process form $_POST, separate configuration and template files, use var_dump ($_SERVER) to view server information, and then you can expand routing, automatic loading and PDO database connections. Master these core architectural principles and be able to build scalable, secure, and easy-to-maintain PHP applications starting from small projects.

So you've decided to dive into PHP — welcome to one of the most widely used server-side languages on the web. Whether you're building a simple contact form or planning to scale up to a full content management system, understanding PHP's architecture from the start will save you time, confusion, and bad habits down the road. Let's break it down in a way that makes sense, even if you're just stepping off the client-side (HTML/CSS/JS) ledge.

How PHP Actually Works Behind the Scenes

When someone says "PHP runs on the server," what does that really mean?

Imagine a user types your website's URL into their browser. Instead of sending them raw PHP files (which would be useless in the browser), the server processes the PHP code first. It executes things like database queries, user authentication, or dynamic content generation, then outputs plain HTML back to the browser.

Here's the flow:

• User requests page.php
• Web server (like Apache or Nginx) sees the .php extension
• PHP engine (like PHP-FPM or mod_php) runs the code
• Final HTML result is sent to the user
• User never sees the PHP — just the result

This separation is key: PHP is invisible to the front end . It does its job behind the curtain.

The Core Building Blocks of PHP Architecture

You don't need a framework on day one, but you should understand the foundational pieces that make PHP scalable and organized.

1. Request Handling

Every PHP script starts with a request. Whether it's a page load or an API call, PHP accesses data via superglobals like:

• $_GET – for URL parameters
• $_POST – for form submissions
• $_SESSION – for user-specific data
• $_SERVER – for environment and server info

Keep in mind: never trust input. Always validate and sanitize $_GET and $_POST data — it's the first rule of secure PHP.

2. Separation of Logic and Presentation

Early PHP often mixes HTML and PHP like this:

 <?php
$user = "John";
?>
<h1>Hello <?php echo $user; ?></h1>

That's fine for learning, but quickly becomes messy. As you grow, aim to separate:

• Logic (data processing, business rules)
• Presentation (HTML output)

Even without a framework, you can do this manually:

• Use PHP files for processing
• Include template files that only display data

This small habit makes your code easier to debug and test.

3. Autoloading and File Structure

As your project grows, you'll have multiple files: classes, functions, config files. Instead of require -ing everything manually, use autoloading (PSR-4 standard is the modern way).

For example, with Composer:

 {
  "autoload": {
    "psr-4": {
      "App\\": "src/"
    }
  }
}

Now, when you instantiate a class like new App\User() , PHP automatically finds src/User.php . No more require_once spaghetti.

Starting Simple, But Thinking Ahead

You don't need Laravel or Symfony to start — but you should think about structure early.

Here's a beginner-friendly project layout:

 /project-root
│
├── public/
│ └── index.php # Entry point (only public-facing)
├── src/
│ └── User.php # Classes go here
├── config/
│ └── database.php # DB settings
├── views/
│ └── home.php # HTML templates
└── composer.json

Key idea: only public/ should be accessible from the web. This keeps your source code safe.

A Few First Steps to Take Now

If you're just starting, focus on these:

• [ ] Install PHP locally (use XAMPP, MAMP, or Laravel Valet)
• [ ] Get Composer working (essential for modern PHP)
• [ ] Write a script that handles a form with $_POST
• [ ] Try including a config file and a template separately
• [ ] Use var_dump($_SERVER) to see what's available

Once you're comfortable with that, explore:

• Simple routing (map URLs to functions)
• Basic autoloading with Composer
• Connecting to a database with PDO

Basically, PHP's architecture isn't about complexity — it's about control. You're running code where it belongs: on the server, securely, with full access to data and system resources. Start small, keep things organized, and let the structure grow with your understanding.

That's how you build something that scales — without rewriting everything twice.

The above is the detailed content of Decoding the Server-Side: Your First Steps into PHP's Architecture. For more information, please follow other related articles on the PHP Chinese website!