What Is PHP? Your Ultimate Guide to PHP

PHP, or Hypertext Preprocessor, is a popular server-side scripting language used mainly for web development to create dynamic web pages.

PHP is open-source, which means you don’t need to purchase a license to use it. It’s also well-supported, with extensive documentation and a massive community of developers.

This scripting language favors web development mainly because of its ease of use, flexibility, and efficiency. No wonder many popular websites, like Facebook, Wikipedia, Slack, and WordPress, use PHP to handle their backend processes.

In this section, we’ll dive into the fundamentals of PHP, specifically its historical background, how it compares to other programming languages, an overview of its syntax and basic structure, and the differences between server-side and client-side scripting. Let’s get right into it.

Historical Context: Origins and Evolution

Created in 1994 by Danish-Canadian software developer Rasmus Lerdorf, PHP originally started as a set of Common Gateway Interface (CGI) binaries written in C.

Initially, creating a powerful scripting language wasn’t part of the plan; Lerdorf just wanted something to monitor visits to his online résumé. So, he gave it the name “Personal Home Page Tools.”

But this tool proved to be more powerful than he initially thought. For context, here’s an overview of some major milestones in PHP’s evolution from a monitoring tool to one of the most used programming languages globally.

Today, about 18 percent of software engineers across the world use PHP for web development. Another study found that about 810 million websites run on PHP. At the time of writing, the latest version of PHP is PHP 8.3, released on November 23, 2023.

PHP vs. Other Programming Languages

One of the primary reasons PHP stands tall against other popular programming languages, like Python or JavaScript, is that it is simple, flexible, and easy to integrate with HTML. While HTML is not really a programming language, it’s the second-most popular markup language among developers.

Python’s versatility and JavaScript’s client-side capabilities aside, PHP still floors these two when it comes to server-side scripting. That explains why it is a go-to choice for building dynamic and interactive web pages.

Syntax Overview and Basic Structure

PHP syntax is straightforward and quite easy to learn, especially if you know a thing or two about C or JavaScript programming languages. A PHP script usually starts with and ends with ?>.

You can write your PHP code within these tags. The code can contain data types, including integers, floats, strings, and arrays, and follows a clear and logical structure that helps create clean and maintainable code.

Later in this article, I’ll show you an example of how PHP code looks with the opening and closing tags I mentioned earlier.

Server-Side Scripting vs. Client-Side Scripting

Now, when dealing with scripting languages, you’ll likely hear these two common phrases: server-side and client-side. Here’s what they’re all about.

Server-side scripting, like PHP, involves code that runs on the server. It generates dynamic content before reaching the user’s browser.

We usually use this type of scripting for tasks like database management, user authentication, and overall dynamic content generation.

Client-side scripting languages, like JavaScript, are quite the opposite. They execute directly in the user’s browser to create interactive web pages.

A good example of this client-side scripting is when you click a button that triggers a JavaScript function to display an alert message.

Learning PHP is fun, especially if you want to create dynamic web applications. As we saw earlier, this language is not only easy to learn but also widely used by both beginners and seasoned developers. Let’s explore some tips to get you started.

Setting Up a PHP Development Environment

To set up your PHP development environment, follow these steps:

1. Install a local server stack

Download and install a local server stack that includes Apache (the server), MySQL (the database), and PHP.

For demonstration purposes, I’ll use MAMP.

Select the MAMP download that’s compatible with your operating system. During the setup process, click “Next” when prompted, accept the terms and conditions, and select the location where you want MAMP installed.

Once the setup is complete, click “Finish.”

Pro tip: You can create a desktop shortcut during the installation process for easier access to MAMP.

2. Start the Local Server

Locate and launch MAMP by clicking “Start” and then click “Allow access” if prompted.

3. Create a Project Directory

Find the htdocs folder in the location you installed MAMP, and create a new folder for your project.

In this example, we’ll name our folder “test.”

4. Create a PHP File

Inside your project folder, create a new PHP file, for example, “test.php.” Right-click on the newly created file and select “Edit with Notepad.”

Writing Your First PHP Code

Now, let’s write our first PHP code. Remember when we mentioned the basic structure earlier in this article?

To recap, we talked about PHP having the following opening and closing tags: and ?>. Then, inside these tags, you can write your PHP code. For example, to output “Hello there!” you would write:

The echo statement is what we use in PHP to output one or more strings to the browser or general HTML content dynamically.

6. Access Your Project in a Browser

Open a web browser. Enter the path for the file as a URL: http://localhost/test/test.php

You should see the output “Hello there!” indicating that your PHP environment is set up correctly.

In the URL above, “localhost” is the local development environment you’ve just created. The first “test” is the folder you created, and “test.php” is the PHP file inside the test folder.

This tells the server to go to your test folder, locate the PHP file, and then print its contents to the browser.

One of the reasons most developers use PHP to create dynamic and interactive web applications is that it supports various data types, operators, control structures, functions, and arrays. In this section, we’ll examine its core features and functionalities.

Variables and Data Types

PHP supports data types such as integers, floats, strings, and arrays. In PHP, we declare variables using the “$” symbol, as shown below.

In the screenshot above, we have declared both the string and array variables using the “$” symbol.

Operators and Expressions

This scripting language also uses operators for arithmetic, comparison, and logical operations. Here’s how to use operators and expressions in PHP:

Note that we use the double forward slash symbol to write comments inside our code. The PHP code should work just fine even without these symbols.

Control Structures

We can also write control structures like conditional statements and loops in PHP to manage the flow of the program. Here’s how to go about it:

In the conditional statement, the code checks if variable $a is greater than variable $b. It then outputs a message indicating whether $a is greater than or not greater than $b.

In the loop statement, the code loops from 0 to 4, outputting the text “Number: ” followed by the current loop index value for each iteration. For example, the first loop would output “Number: 0.”

Functions and Methods

We use functions in PHP to encapsulate reusable code blocks. Methods, on the other hand, are functions defined within classes in object-oriented programming.

We’ll talk about object-oriented programming shortly. For now, let’s look at functions and methods in action:

The code above is a function that greets the user by their name. In that case, the output would be “Hello, Alice!”

Arrays and Associative Arrays

Arrays in PHP can be indexed or associative. If you opt for an indexed array, you’ll access the value of each variable using its index. One rule that you should always keep in mind is that in computer programming, we start counting from index “0,” then “1”, then “2,” and so forth.

Associative arrays, on the other hand, have named keys that you use to access data in the array. I know this sounds a little bit confusing, so let’s look at examples of PHP code containing indexed and associative arrays:

The indexed array will output “Apple” because it is the first item in the array. Remember, we said that in programming, we begin to count from zero, not one. In the associative array, “25” is the output because we’ve specifically asked the code to echo the value of Alice’s age.

Alice and Bob are the keys in this case. We can use them to unlock any data they’re associated with.

In PHP, we use Object-Oriented Programming, simply known as OOP, to organize code by grouping related properties and methods into classes and objects.

OOP has its own principles, such as inheritance, encapsulation, and polymorphism, that make code reusable and maintainable. Here’s OOP in a nutshell:

Introduction to OOP Concepts

OOP in PHP revolves around classes and objects. You can think of a class as a blueprint and an object as an instance of that class.

The code above defines a “Car” class with a property of “$color” and methods to set and get the color. It then creates an object of “Car” and sets its color to “red.” Finally, we print the color we’ve just created.

Classes and Objects

Classes define the structure, while objects are instances of classes. Here’s an example:

This code defines a “Person” class with a property “$name.” We then created a method to say hello.

To make the code work, we create an object of “Person” and then give it the name “John.” That’s where the output “Hello, I’m John” comes from.

Inheritance and Polymorphism

Inheritance allows a class to use the properties and methods of another class. Basically, it “inherits” these properties and methods, hence the name.

In the code above, we’ve defined an “Animal” class with a “makeSound” method. The “Dog” class extends “Animal” and overrides the “makeSound” method. It then creates an object of “Dog” and prints “Bark.”

Encapsulation and Abstraction

Encapsulation hides the internal state and requires interaction through methods, as shown in the screenshot below:

We’ve created a class and gave it the name “BankAccount with a private “$balance” property. We’ve also provided methods to deposit money and get the balance. Next, we create a new object and name it “BankAccount,” deposit money into it, and then print the new bank account balance.

Interfaces and Traits

Interfaces define methods that must be implemented. On the other hand, traits include reusable methods.

We’ve defined the “Logger” interface and created a “SimpleLogger” class that implements it. On top of that, we define “MessageTrait” and use it in the “User” class. Finally, we create objects of “SimpleLogger” and “User” and then call their methods.

PHP libraries and frameworks provide prebuilt modules and tools that speed up coding processes, enhance security, and promote best practices during web development. As a result, developers can shift their attention to creating unique features instead of trying to reinvent the wheel.

Overview of Popular PHP Libraries

In this section, we’ll briefly go over the most popular PHP libraries and their roles.

Guzzle

Guzzle simplifies HTTP requests and integrations with web services. This makes it easy to send requests, handle responses, and manage errors.

Swift Mailer

As the name implies, we use Swift Mailer to send emails from PHP applications. This library supports various transport methods and comes with advanced features like file attachments and HTML content.

Introduction to PHP Frameworks

You’ll find many different PHP frameworks out there, but Laravel, Symfony, and CodeIgniter are among the most popular.

Advantages of Using Frameworks in PHP Development

In programming, having a framework is like using a prebuilt frame for a house instead of building one from scratch out of lumber and screws. Of course, that alone comes with many benefits, as you’ll learn below.

• Rapid development: This one is pretty obvious – because frameworks provide prebuilt modules and tools, they help speed up the development process.
• Enhanced security: Frameworks usually come with built-in security features to protect against common vulnerabilities like SQL injection and CSRF attacks (we’ll talk about this shortly). As a result, you won’t need to set up security features from scratch every time you use a framework on your project.
• Maintainable code: They also promote best practices and organized code. This trait makes PHP easier to maintain and scale.
• Community support: Popular frameworks, like those we’ve discussed so far, have large communities. The presence of a large community also means extensive documentation, tutorials, and forums for support.

The whole point of using PHP frameworks is to allow you to focus more on the unique aspects of your application. That’s because frameworks are designed to handle repetitive tasks. After all, they mostly contain pre-written functions.

Integrating databases is one of those things you can’t really avoid when creating dynamic web applications with PHP. Database integration allows you to store, retrieve, and manipulate data efficiently.

As a result, you can enable features like user authentication, content management, data analysis, and more.

Connecting PHP With Databases

Here’s how to connect PHP with databases.

1. Install and configure the database: Make sure you have a database like MySQL installed and configured on your server.
2. Create a database and table: Use SQL commands to create a database and a table where your data will be stored. For example, in this MySQL tutorial, the user creates a database with a table that stores the first name, last name, username, and roll number.

3. Connect to the database: Use PHP Data Objects (PDO) or MySQLi to establish a connection to the database.

Once the connection has been established, you can now execute SQL queries using the connection object to interact with the database.

Common Database Operations

As you would expect, many different operations happen in databases. In this section, we’ll look at four of the most common: create, read, update, and delete, or CRUD, as commonly referred to in web development.

• Create: Inserts — or rather, creates — new records into a database. Think of it as adding new data to your tables.
• Read: Retrieves data from the database. It asks the database to fetch records that match certain criteria.
• Update: Modifies existing records in the database. For instance, this is the operation that kicks in when you want to update a user’s email address.
• Delete: Removes records from the database. A good example of how this operation works is when you want to remove a user who no longer exists in your system.

Note that the operations we’ve discussed above have specific HTTP protocols. For example, POST represents the create operation, GET is for read, PUT is for update, and DELETE is for delete.

Introduction to SQL Injection Prevention

SQL injection prevention involves implementing techniques to protect your database from malicious SQL code injected by attackers.

Here, we use prepared statements and parameterized queries to ensure that user inputs are safely handled and not treated as executable code.

Think of a scenario where an attacker injects harmful code into the system. If the database isn’t configured correctly with SQL injection prevention, it will likely execute the injected code.

Now, let’s look at it from a different perspective: with proper SQL injection prevention, the database will treat the malicious code as data, so there is no need to execute it.

So far, we’ve seen that web development with PHP allows you to create dynamic, interactive websites and applications by leveraging its server-side scripting capabilities.

Let’s now dive a little bit deeper into what actually happens during different phases of the web development process.

Introduction to Web Servers and PHP

Since PHP is a server-side language, it works with web servers like Apache and Nginx to process server-side scripts and serve dynamic content to users.

These servers interpret PHP code within webpages and execute it to generate HTML content and then display it on the user’s browser.

Creating Dynamic Web Pages With PHP

We also mentioned that we can use this programming language to create dynamic web pages. To do this, you’ll need to embed PHP code within HTML.

Integrating PHP with HTML is a great way to generate content on the fly based on user interactions, database queries, or other server-side processes.

Form Handling and Data Validation

You can also use PHP to handle form submissions and validate user input. This helps ensure data integrity and security.

PHP can collect form data, check for errors or malicious input, and process the validated data for storage or further actions. This is where the importance of injection prevention comes into play.

Session Management and Cookies

PHP has powerful tools like $_SESSION for session management and setcookie() for handling cookies. With these tools, you can track user activity, store preferences, and maintain state information across multiple pages.

It’s important to ensure that your PHP applications are secure. This not only protects sensitive data but also helps maintain user trust. Like in any ecosystem, the best way to implement strong security measures is to first understand possible vulnerabilities.

Sanitizing User Inputs

Sanitizing user inputs is the process of cleaning and validating data entered by users. This strategy helps prevent malicious code from being executed.

To sanitize user inputs in PHP, we use functions like htmlspecialchars() and filter_var() before processing or storing the inputs. The htmlspecialchars() converts special characters in a string to their corresponding HTML entities.

As a result of this conversion, characters like , >, &, and “ are displayed as text, not HTML or JavaScript. On the other hand, we use filter_var() to verify that the data from the user meets certain criteria, such as being a valid email address, URL, or even number.

That way, anything that doesn’t meet that criteria isn’t accepted into the system.

Authentication and Authorization

It’s also possible to implement strong authentication mechanisms to verify user identities and proper authorization checks to ensure users have permission to access specific resources or perform certain actions.

To achieve this, you’ll need tools such as password hashing (password_hash()), session management, and role-based access control.

Using HTTPS for Secure Communication

Using HTTPS is a great way to secure communication between the user’s browser and the web server. This method encrypts data transmitted over the network.

When setting up your hosting environment, you’ll need to obtain and install an SSL/TLS certificate on your server to enable HTTPS. A website with an active SSL certificate has a padlock icon next to its domain on the web browser.

Pro tip: In some browsers, such as newer versions of Google Chrome, you’ll need to click on the tune icon to see the security status of that particular domain.

PHP, like most programming languages, needs a little bit of tweaking here and there to improve performance. This is particularly important when creating resource-intensive applications. Here are some proven optimization strategies you may want to try out.

Caching Strategies

Caching is creating copies of data and storing them in a temporary location away from the original source. That way, when a user requests this data, it loads from the temporary location rather than the original source.

When using PHP, you can implement caching strategies like using APCu for opcode caching, Memcached or Redis for data caching, and leveraging HTTP caching headers.

Code Optimization Tips

Writing PHP code isn’t enough, although it’s for sure a great place to start. To improve its performance, you’ll need to implement some optimization techniques.

One way of doing this is by minimizing the use of loops since each loop may have high resource usage. You should also avoid unnecessary computations, use built-in functions efficiently, and employ autoloaders to load classes on demand.

Load Balancing and Scalability

Load balancing is a common technique web hosting providers use to improve server performance. This technique distributes incoming traffic across multiple servers. As a result, your PHP applications will be highly available, reliable, and scalable.

PHP continues to maintain its relevance even in modern development ecosystems. That’s because it’s very versatile, as you’ll learn below.

Integration with Frontend Technologies

Because this language integrates well with frontend technologies like JavaScript frameworks (e.g., React, Angular, Vue.js), it makes it possible to build dynamic and interactive web applications. It acts as the backend that handles data processing and storage.

Microservices and API Development with PHP

In modern web development, we use PHP for microservices architecture and API development. With this language, you can build modular and scalable applications using frameworks like Lumen or Slim.

Serverless Computing and PHP

Serverless computing is a way of running code without managing servers. This is made possible by using platforms like AWS Lambda and Bref to deploy PHP functions that scale automatically and reduce operational complexity.

We’ve covered the basics of PHP, but there’s still a lot more to learn. You can enhance your PHP skills by exploring a variety of resources.

Here are our top recommendations:

Community forums: You can find tons of valuable information in forums like Stack Overflow, PHP Forum, and Reddit.

These resources can help deepen your understanding of PHP, stay updated with the latest trends, and connect with fellow developers for continuous learning and improvement.

The future of PHP development looks very promising. To begin with, it’s safe to say that PHP has no real competitor when it comes to server-side programming, at least for the foreseeable future.

One study found that about 76.2% of websites use PHP as their preferred server-side programming language. The closest competitor, ASP.NET is several planets away – only 6.1% of websites use this technology.

We’re also seeing a trend where artificial intelligence is taking over the web development process. From creating smart chatbots to voice search optimization, PHP will partner with AI to improve the development process and create powerful applications that users will enjoy.

And it’s not just about AI — businesses are also evolving in different dimensions, especially toward the cloud. Things like serverless computing, cloud integration, cybersecurity, and even voice search optimization all circle back to PHP in one way or another.

That brings us to our conclusion: PHP is here to stay. Because of its versatility and popularity, PHP is one of those programming languages you won’t regret learning.