A Look Under the Hood: How PHP Works from Start to Finish

How PHP Works: An Overview of Its Functions

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PHP (Hypertext Preprocessor) is an open-source, server-side scripting language. A scripting language is a program that contains lines of code (script) to automate tasks.

PHP is one of the earliest programming languages, but it is the most preferred for the development of web applications. It can also be used for creating client-side applications, like desktop applications.

PHP is available for everyone to download and use. It is also quite simple to learn. Moreover, PHP can be used for many functions. It is the underlying language behind databases, websites, DIY website builders and more. This article will discuss the basic principles and functionality of PHP web development.


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  • PHP is an open-source server-side scripting language web developers use to build web applications
  • PHP is included in virtually all web development stacks because of its interoperability
  • The immense support that PHP receives makes it possible for developers to solve technical issues quickly and reliably
  • PHP supports the most popular commercial and open-source databases
  • PHP supports procedural (functional) and object-oriented programming styles

Importance Of Understanding How PHP Works

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PHP offers many benefits to those learning how to use it. It is an open-source, feature-rich language that provides all the functionality you can get from a proprietary or paid scripting language. As a PHP developer, you will be in demand by many IT companies looking for PHP developers. Here are the most important reasons to understand how PHP works in web development.

1. Writing Efficient Code

PHP is a lightweight programming language that allows you to write efficient code. These codes will run faster, perform better, and use fewer system resources. Understanding the basis, such as variables, data types, and PHP functions, will help you create manageable, debuggable, and scalable applications.

Anyone looking to create a great user experience on a website or server-side application should learn PHP.

2. Debugging and Troubleshooting

One benefit that PHP offers developers is the ability to identify and troubleshoot issues in code. It is easy for developers to inspect PHP scripts and identify errors or bugs that could create unsavory results. After becoming familiar with PHP’s logging and error-reporting functions, you will become more adept at identifying and debugging issues.

3. Security

PHP is ideal for those looking to design secure applications. It offers many functions to help you sieve user inputs to prevent malformed or malicious inputs from disrupting the code. It also processes requests in a way that promotes the security of secure web applications.

By learning to utilize PHP’s built-in security functions and libraries, you can secure your applications from attackers, such as cross-site scripting (XSS) and SQL injection. Furthermore, you can use the permissions and file system functions to prevent unauthorized access to sensitive data.

4. Interoperability

PHP is included in virtually all web development stacks because of its interoperability. Developers can use it with programming languages like HTML, JavaScript, and CSS. For instance, adding PHP in HTML gave rise to dynamic websites. HTML on its own can only generate static websites. Combining these technologies allows web developers to produce a more seamless user experience.

Since PHP is open-source and has massive community support, it has many frameworks and tools for developers. Developers learning PHP’s standard libraries and extensions can incorporate third-party frameworks and tools into their processes.

Basic Principles of PHP

PHP is an open-source server-side scripting language web developers use to build web applications. The basic principles of PHP include the following:

1. PHP Is an Open-Source Language

An open-source programming language is freely available to use and modify (depending on the open-source license). Since no one owns PHP, the maintenance of the language is the community’s responsibility. PHP’s immense community support allows developers to solve technical issues quickly and reliably. This feature attracts more developers, increasing the development and popularity of the PHP programming language.

2. PHP Is a Server-Side Language

A server-side programming language is a scripting language that runs on a web server. When you want to view the page, your browser sends a request to the web server. The server processes the request and sends the webpage content. It is called server-side scripting because most of the processes happen on the backend of your website. This feature makes PHP different from client-side scripting languages like Angular, Vue, and JavaScript,

3. PHP Code Is Embedded in HTML

A PHP script resides in an HTML file and is contained within special tags (<?php and ?>). However, the file is saved with the .php extension, not the .html extension. Since the PHP code is embedded in the HTML page, you can call that page a PHP program. The HTML and PHP codes combine to produce the content and functionality of the webpage.

4. PHP Supports Various Databases

PHP supports the most popular commercial and open-source databases. Some of the most popular databases it supports are MySQL, Oracle, and PostgreSQL. Those databases fall under relational database systems. They serve as the backbone for most modern websites.

Developers use these databases to store user data, product reviews, purchase histories, shopping cart information, credit card numbers, and the web page.

5. PHP Supports Object-Oriented Programming

PHP supports procedural (functional) and object-oriented programming styles. Object-oriented programming (OOP) is a programming paradigm that relies on the concept of classes and objects. It structures a programming language into code blueprints that can be applied in multiple instances. OOP is favored over its counterpart, functional programming, as the standard way for programmers to create web and software development applications.

6. PHP Is Easy To Learn

Anyone with a basic understanding of HTML can learn PHP. Beginners will notice many similarities between HTML and PHP, especially in syntax and built-in functions. This feature makes PHP one of the simplest programming languages. Anyone interested in web development can begin using PHP immediately if they understand basic HTML.

7. PHP Is Continuously Evolving

The PHP community maintains PHP. This community constantly offers tools and patches to make the language faster, easier to use, and more efficient. This constant evolution is why PHP remains one of the best programming languages despite the emergence of other great options. As a developer, you must stay updated on the latest updates and improvements to get the most out of the PHP programming language.

The Functionality of PHP

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PHP is an open-source server-side scripting language used to create dynamic web pages. It is a server-side language because the processes happen on the server’s backend. This feature makes it different from client-side browsers like JavaScript. Let’s look at some functionalities of PHP:

1. Dynamic Content Generation

Dynamic web pages allow website owners to deliver content based on a predefined set of rules. Such pages are built using server-side languages such as PHP. PHP is the most preferred server-based language for dynamic web pages. It is used by top websites such as WordPress and Facebook and is the underlying technology behind DIY website builders.

Using PHP, web developers can create dynamic content that offers a customized and personalized website experience for a specific user.

2. Form Handling

Forms are essential to websites. They are used to restrict access to unauthorized users, collect user data and enhance website functionality. While web forms are created using HTML, developers use PHP to transport and process the values provided by the user. Developers also use PHP to sort relevant data, weed out malformed data and keep the information system clean and organized.

3. Database Integration

PHP is compatible with over 20 databases. Using PHP, Web developers can connect with supported databases via PHP’s MySQLi extension or with PHP Data Objects (PDO). Developers and authorized users will add data, perform queries, and retrieve data through this database integration. The most popular database used with PHP is the MySQL database.

4. Session Management

PHP session management functions allow developers to build and manage session-based applications. These functions can be used to initialize sessions and register sessions. Session Management is important because it enables users to securely interact with web applications without constantly re-authenticating. Any website or web application requiring users to log in before performing certain operations needs the PHP session management functions.

5. Server-Side File Management

File Management involves creating an organized structure for storing information to facilitate easy retrieval. Typically, website information is stored on the server. With the PHP server-side management function, developers can store, organize and access files without compromising security.

Authorized users can reorganize, read or delete files stored on the website’s backend.

6. Object-Oriented Programming

Object-oriented programming (OOP) is the standard choice for beginner and experienced developers. PHP supports the four principles of OOP (abstraction, inheritance, encapsulation, and polymorphism). Developers can build testable, flexible, and maintainable code when they use OOP correctly in conjunction with PHP. These codes will be reusable and easy to read.

7. Web Application Frameworks

PHP allows developers to create dynamic websites, manage files, and track sessions. However, creating PHP scripts from scratch can be complicated and time-consuming. PHP developers instead use PHP frameworks to make these processes more efficient and streamlined. There are a variety of supported web application frameworks in PHP, like Laravel, CodeIgniter, Symfony, and CakePHP

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Components of PHP

PHP is a powerful language for developing web applications due to its impressive components and broad functionality. Here are some of the leading PHP components:

1. Core

Core PHP is the basic PHP programming language. The Core engine interprets and executes PHP codes to create dynamic web pages. The critical difference between Core PHP and a PHP framework is that Core PHP can work independently. Any developer who understands the basic principles of PHP scripts can build web applications using core PHP.

The Core PHP also offers a wide variety of functionality to allow developers to create flawless blocks of code that can be managed and reused.

2. Extensions

PHP extensions refer to special plugins or libraries that add functionality to the Core PHP. Developers use these extensions to avoid rewriting the same code for different applications. Many extensions in the public domain exist for differences, such as database access, encryption, and image manipulation. You can add publicly available extensions to your PHP binary application or create your own.

3. Zend Engine

The Zend Engine is a crucial component of PHP. It provides the environment for interpreting and running PHP scripts. The most vital element of the Zend Engine is the Zend Virtual Machine. This machine comprises the Zend Compiler, Zend Executor components, and sometimes the OPcache Zend extension. These three components form the heart of PHP and execute PHP scripts.


SAPI stands for Server Application Programming Interface. It is API developers use to interact with web servers and other server environments and extend the web server capabilities. SAPI is also called Internet Server Application Programming Interface (ISAPI) by Microsoft and Netscape Server Application Programming Interface (NSAPI) by the defunct Netscape web server.

5. Libraries

Although PHP is a powerful and efficient language for writing code, creating codes for each process can become tedious and time-consuming. Instead of writing code from scratch for each function, developers turn to PHP library airs. PHP libraries are collections of code templates for specific functions. These libraries reduce the developer’s load and manage common tasks such as sending emails, working with XML, and accessing files and directories.

6. Database Drivers

A database driver is a program that connects an interface to a specific database via a protocol (ODBC or JDBC). Developers use database drivers to connect the PHP interface with many types of DBMS (database management systems), such as MySQL or Oracle.

If the developer connects to a java application, they use the JDBC (Java Database Connectivity API) driver. If the connection is to individual databases, the developer needs to use drivers specific to each database type.


PHP-FPM (FastCGI Process Manager) is commonly described as a PHP for high-traffic websites. It works as a separate process manager for PHP-based websites to offer better performance and scalability. It is the perfect option for developers who are developing high-traffic websites. Its key features include its fast processing times and low memory consumption.

Other features that make it a better alternative to the FastCGI implementation of PHP for high-traffic websites include its advanced management, stdout and stderr logging, and accelerated upload support.

How Does PHP Work with HTML?

In this section, we will show you how PHP works with HTML. PHP is a server-side scripting language, so it is executed on the server. The script output is built on the server, which sends the result as HTML to the client’s browser. A PHP file contains a mix of PHP and HTML code. Here is how PHP works with HTML:

1. The PHP Code Is Embedded in HTML

PHP codes within HTML content must be enclosed using the unique tags <?php and ?>. Any code inserted between these two tags is considered PHP code and executed on the server file before the output is sent to the client’s browser. Note that for this to work, you must save the file with a .php extension.

2. The Web Server Executes the PHP Code

The web server will detect that the HTML page contains PHP code. The PHP code will be interpreted and executed on the server side and then merged with the HTML. The final output (HTML webpage) will be sent to the client browser for rendering.

3. The PHP Interpreter Executes the PHP Code

The PHP interprets the functions within the PHP code. It can perform various tasks, such as accessing information from a database, processing user input, or generating dynamic content. When it is done interpreting the code, it will then create an HTML output.

The PHP interpreter reads the PHP code and executes it. It can perform various tasks, such as connecting to a database, processing form data, and generating dynamic content.

4. The PHP Code Generates HTML Output

After the PHP interpreter has executed the code, an HTML output will be generated. The output will always be generated in every instance. If the code works fine, it will be the desired output. If the code has an issue, the output will be an error message.

5. The Web Server Sends the HTML Output to the User’s Browser

The client browser receives the HTML output from the web server. It will then render the output on the page. All processes occur at the server end (website backend).

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Best Practices for Working with PHP

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Are you excited about working with PHP? Here are some best practices to keep in mind. These tips will help you write better code and reduce errors.

1. Follow a Coding Standard

The first step is to adopt a coding standard. Following a coding standard makes your code easier to interpret, debug and maintain. A team of lead developers agreed upon the current coding standards to make PHP frameworks and libraries easier to combine for users. This team is the PHP Framework Interop Group (PHP-FIG). The group is responsible for the PHP Standards Recommendations (PSRs).

There are many standards, but we recommend using either the PSR-1 or PSR-2. The PSR-1 is the basic coding standard that every beginner should know. It follows single guidelines and naming conventions. The PSR-2 is an updated version of the PSR-1 coding standard. It has a more expanded coding style guide and requires all the rules of the PSR-1 coding standards.

2. Use a PHP Framework

PHP is a powerful scripting language, but core PHP might not be suitable for handling complex business requirements. It can be challenging for most developers to generate and manage PHP codes for complex applications. The increased requirement and skill sets make the project strenuous, time-consuming, and expensive.

A better approach is to integrate PHP frameworks into your workflow. Frameworks are pre-built components and libraries that allow you to manage specific tasks. They allow you to handle common tasks without writing code from scratch and reduce the complexity of web development projects. There are dozens of PHP frameworks, but the most popular are Laravel, CakePHP, Zend Framework, and Yii Framework.

3. Sanitize Input Data

You must create functions to sanitize user inputs to protect your projects. Failure to do so will make your application vulnerable to SQL injection (SQLi) and other security threats. SQLi is a type of injection attack that gives rise to the execution of malicious SQL statements. Attackers use these injections to bypass existing security measures and take control of the database server.

However, the only way such attacks can successfully take place is when you allow user input to enter the system without sanitizing them. If you are not careful, criminals will use it to tamper with your database.

4. Use Version Control

Version control helps you track changes in your code. If something goes wrong, you can compare changes in different versions and retire the code to a version you can work with. Developers need to use version control, especially when part of a team working on the source code. To do this, you need Version Control Software (VCS).

Version Control Softwares are tools developers use to keep track of the various source codes they are working on. They are also called SCM (Source Code Management) tools or RCS (Revision Control System). The most prevalent Version Control Software is Git. Other noteworthy alternatives are CVS, SVN, Mercurial, and Monotone. You can also use a hosted Version Control Service like GitHub or Bitbucket.

5. Use Caching

A cache is a file that contains a collection of duplicate data. The cache is stored in a location that is easily accessible to the developer, while the original data source is usually stored in another location. The benefit of caching is that it minimizes page generation time and other expensive operations.

There are two types of caching in PHP: output caching and parser caching. Output caching stores the data in a location that can be accessed by another script faster than it can generate it. Parser caching is a specific feature that minimizes the time it takes to parse a PHP file. Both caching types can help boost the performance of your PHP application.

6. Optimize Database Queries

Databases are an essential programming element as they help create, update, and delete data. However, as the data volume increases, accessing data from databases can become time-consuming and create a bottleneck for PHP applications. To prevent this from happening, you need to optimize databases properly and timely. Property database optimization improves the end-user experience and lowers infrastructure costs.

There are many ways to optimize database queries. Best options include using indexes to speed up queries, limiting the number of queries, and avoiding using SELECT queries.

7. Use Error Handling

Like all programming languages, PHP presents the possibility of errors. Error Handling Success means that you can catch errors quickly and take appropriate actions. If you don’t implement error-handling processes, these errors can lead to unforeseen consequences.

Thankfully, handling errors in PHP is straightforward. The default mode involves displaying the file name, line number, and error type on the default page. There are two ways to handle PHP Errors: The Die() method and Custom Error Handling. The Die() method is the default error handling method, while the Custom Error Handler is a custom-made function usually called when an error has occurred in PHP.

8. Write Secure Code

Writing secure (clean) code will benefit you in your current and future projects. PHP is an old programming language. Over the years, attackers have fine-tuned different ways to attack PHP and gain unauthorized access. Writing secure codes will ensure that your web applications are out of the reach of malicious attacks.

On the other hand, secure codes will also make others willing to collaborate with you. When you build secure applications that stand the test of time and can fend off multiple security attacks, it will be easy to do well in the programming world.

9. Test Your Code

Testing your code is more than just a good principle. It is something every developer should do. Unfortunately, many developers go out of their way to avoid it. One benefit of testing your code is that it prevents bugs from creeping into it. You can detect little things, such as wrong values or syntax errors, that can become impossible to notice when you have compiled the entire code.

Furthermore, if you treat each blog before moving to the next, you will have a realistic approach to how your code will pan out when displayed on the client web browser. This approach will make you write efficient code that improves customer experience and makes deployments smooth.

10. Document Your Code

Code documentation is very vital for many reasons. The key reason is that it is a reference point for you and other developers wanting to review and update your code. You can use tools like PHPDoc to document your code, including code tests, so that other developers can understand and use your code effectively. It would help if you create documentation, such as README files, to help others understand how to use your application.


PHP is an excellent programming language for anyone looking to become a web developer. It offers robust features, powerful functionality, and wide versatility. It supports numerous databases, frameworks, and operating systems. It is the underlying language between the best website builders and is supported by all the best website hosting providers. Given its broad reach and usefulness, it is easily a recommended language every web developer should learn.

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Next Steps: What Now?

Further reading – Useful Resources

Frequently Asked Questions

Frequently Asked QuestionsWhy use PHP?

PHP is a server-side scripting language that allows web developers to create dynamic content and interact with databases. It is widely used for its simplicity, speed, and flexibility. It is available on all major operating systems, including Windows, Linux, and Mac. Anyone looking to write dynamic web pages quickly should consider using PHP.

Why is the PHP community important?

PHP is an open-source programming language, meaning no one owns it. The PHP community maintains the PHP language and makes regular upgrades. They also offer excellent support to developers who might introduce issues while using the programming language. The vast collection of tools, libraries, and frameworks that PHP supports are available to the PHP community members.

What is the future of PHP?

PHP has a promising future as the PHP community continues to evolve the language with new features and updates. At the beginning of 2023, PHP had a 49.7% market share, making it the most popular programming language.

What is a PHP script?

A PHP script is a set of instructions that starts with <?php and ends with ?>. This script is embedded into the HTML code and is executed on the server side to produce dynamic web pages. They are created using basic text editors or code-writing software tools. You can place a PHP script anywhere in the HTML document.

What exactly does PHP do?

PHP is a server-side scripting language that can do anything any CGI program can. These include generating dynamic page content, collecting and sorting form data, or sending and receiving cookies. You can also use PHP for desktop applications and command-line scripting.

Does PHP need a server?

Yes. PHP is a server-side scripting language, meaning you won’t be able to run PHP scripts without a web server.

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