Introduction to PHP

Introduction to PHP

PHP is one of the most widely used server-side programming languages for building dynamic websites and web applications. It allows developers to create websites that can process information, communicate with databases, manage users, handle forms, generate dynamic pages, and perform many other tasks that cannot be achieved with HTML and CSS alone.

PHP originally stood for Personal Home Page, but it is now commonly understood as PHP: Hypertext Preprocessor. PHP is an open-source scripting language designed primarily for web development, although it can also be used for other programming tasks.

What Is PHP?

PHP is a server-side scripting language. This means that PHP code is executed on a web server before the resulting content is sent to the user’s browser.

For example, when a user visits a PHP-powered website, the browser sends a request to the server. The server processes the PHP code, performs any required operations, and sends the resulting HTML response back to the browser.

The browser normally receives the generated HTML rather than the original PHP source code.

Client-Side vs Server-Side Programming

Understanding the difference between client-side and server-side programming is important for web developers.

Client-Side Programming

Client-side code runs primarily in the user’s web browser. HTML, CSS, and JavaScript are common client-side technologies.

For example, JavaScript can respond to a button click, modify page content, validate information, or create interactive interface elements directly in the browser.

Server-Side Programming

Server-side code runs on a web server. PHP is one example of a server-side programming language.

Server-side programming can be used to:

• Process form submissions.
• Communicate with databases.
• Authenticate users.
• Manage sessions.
• Generate dynamic HTML.
• Process business logic.
• Read and write files.
• Build APIs and backend services.

How PHP Works

A simplified PHP request normally follows this process:

1. The user enters a website address or clicks a link.
2. The browser sends a request to the web server.
3. The web server identifies the requested PHP file.
4. The PHP interpreter executes the PHP code.
5. PHP performs the required operations.
6. PHP generates an output response, often HTML.
7. The web server sends the response to the browser.
8. The browser displays the resulting webpage.

For example, a PHP script might retrieve a student’s name from a database and generate a personalized dashboard containing that student’s information.

PHP and HTML

PHP can be embedded directly inside an HTML document. This makes it possible to generate dynamic sections of a webpage.

A PHP file normally uses the .php file extension.

PHP code is placed between PHP opening and closing tags:

<?php
echo "Hello, Dwallnet Technologies!";
?>

When the server processes this code, the browser receives the generated output.

Your First PHP Program

A simple PHP program can use the echo statement to display text.

<?php

echo "Hello World!";

?>

The statement displays:

Hello World!

Another way to display output is with print:

<?php

print "Welcome to PHP programming.";

?>

PHP Statements

PHP programs are made up of statements. Most PHP statements end with a semicolon.

<?php

echo "First statement";
echo "Second statement";

?>

The semicolon tells PHP that a statement has ended.

PHP Comments

Comments are notes written inside source code for developers. They are not normally displayed as webpage content.

A single-line comment can be written using two forward slashes:

<?php

// This is a PHP comment
echo "Hello";

?>

PHP also supports the hash symbol for single-line comments:

<?php

# This is also a comment
echo "Hello";

?>

Multi-line comments can be written using /* and */:

<?php

/*
This is a
multi-line comment.
*/

echo "Hello";

?>

PHP Is Case-Sensitive

PHP variable names are case-sensitive. This means that variables such as $name and $Name are considered different variables.

PHP language keywords such as echo are generally not case-sensitive, but developers should follow consistent lowercase conventions for readability and coding standards.

PHP Development Environment

To run PHP locally, a developer needs a PHP-enabled environment. Common local development environments include XAMPP, WAMP, MAMP, and native PHP installations.

XAMPP is particularly useful for beginners because it provides Apache, PHP, MySQL-compatible database services, and other development tools in one package.

A typical XAMPP project can be placed inside the htdocs directory.

For example:

C:\xampp\htdocs\myproject\index.php

The project can then be accessed through a local address such as:

http://localhost/myproject/

PHP and Web Servers

PHP requires an environment capable of processing PHP scripts. A web server such as Apache can work with PHP to process PHP files and return the generated response to the browser.

When developing locally, tools such as XAMPP can provide the web server and PHP environment needed for testing applications before deploying them to a live server.

PHP in Modern Web Development

PHP continues to be used for many types of websites and web applications. It is also the foundation of several important web platforms and frameworks.

PHP can be used to build:

• Content management systems.
• Learning management systems.
• Student portals.
• Business websites.
• E-commerce applications.
• Membership platforms.
• Web APIs.
• Administrative dashboards.
• Custom backend applications.

Popular PHP technologies and platforms include WordPress, Laravel, Symfony, and many custom PHP applications.

PHP and Databases

One of the major strengths of PHP is its ability to communicate with databases.

A PHP application can send queries to a database, retrieve records, create new records, update existing information, and delete records when appropriate.

For example, a student management system could use PHP to retrieve a student’s course information from a database and display it on a dashboard.

Dynamic Websites

A static website normally displays content that remains the same until a developer manually changes the files.

A dynamic website can generate different content depending on the user, database records, submitted information, time, permissions, or other conditions.

PHP makes it possible to create this type of dynamic behavior.

PHP and WordPress

WordPress is a major example of a PHP-powered application. WordPress uses PHP to process requests, load content, communicate with its database, execute plugins and themes, and generate webpages.

Learning PHP therefore provides a strong foundation for developers who want to customize WordPress themes, build plugins, create custom functionality, and understand how WordPress works internally.

Basic PHP Example with HTML

PHP can be combined with HTML to create dynamic pages.

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>PHP Introduction</title>
</head>
<body>

	<h1>My PHP Page</h1>

	<?php
	echo "<p>Welcome to PHP programming.</p>";
	?>

</body>
</html>

The HTML provides the page structure while PHP generates dynamic content.

PHP Coding Best Practices

Even when writing simple PHP programs, developers should develop good habits from the beginning.

• Use meaningful names for variables and functions.
• Indent code consistently.
• Use comments where they improve understanding.
• Keep code organized and readable.
• Validate and sanitize user input.
• Never expose sensitive information unnecessarily.
• Keep PHP and HTML organized where practical.
• Use current, supported PHP versions when developing new applications.

Summary

PHP is a server-side scripting language used to create dynamic websites and web applications. Unlike HTML and CSS, which primarily describe the structure and presentation of a webpage, PHP can process information on the server and generate dynamic responses.

In this lesson, you learned what PHP is, how server-side programming works, how PHP interacts with a web server, how to create a basic PHP script, how PHP can be combined with HTML, and why PHP remains important in modern web development.

In the next lesson, we will examine PHP syntax in greater detail and learn the rules that govern how PHP programs are written.