PHP vs. JavaScript: What's Best for Your Application?

Comparing PHP vs. JavaScript, while a commonly posed comparison, isn't the 1:1 comparison many think it is. In fact, PHP and JavaScript are a frequent pairing for web applications.

While there are cases where JavaScript can be used in back-end applications, and PHP can be used in front-end applications, for the sake of brevity, we’ll be comparing and discussing from the point of view of back-end PHP and front-end JavaScript only. (Node and back-end JavaScript exist, but that comparison deserves its own article.) 

Let's dive in!

PHP vs. JavaScript: Overview

When starting a new project, one of the key decisions is which languages will be used. For Web Applications, PHP and JavaScript rank highly among the best languages to use. 

While these two languages are sometimes compared and even thought of as competitors, prompting the question of PHP vs. JavaScript, they’re actually complimentary languages and are typically used in conjunction to build fast and interactive web applications. In more precise terms, PHP typically handles the back-end while JavaScript handles the front-end.

What Is PHP?

At its core, PHP is a general-purpose, server-side scripting language with a focus for web development. PHP can actually be used to perform virtually any server-side tasks from command line, but it’s typically used for web applications. 

Due to PHP's forgiving nature and start as a procedural language, the PHP learning curve is much lower than other, more strict languages. This can be a double edged sword, because some say that forgiveness leads to ugly code. That’s up to the developer though because over the years, PHP has become a mature, fully-featured, and object-oriented language with many different class structures, annotations, new expressions, community standards, and many other features for writing beautiful code.

In the context of web applications, PHP comes into play when an HTTP request is delegated to it from a web server. Once delegated, the PHP source code is run, and its output is given back to the web server to be served to the user. At that point, PHP’s hands are off. In other words, PHP has no direct interaction with the user. That’s where languages like JavaScript come into play.

What Is JavaScript?

JavaScript, in contrast to PHP, works on the client-side of web applications. It’s a very useful, simple-to-use scripting language that can either be written directly into HTML using script tags or even loaded into the HTML from its own file, similar to how CSS is utilized. 

JavaScript is actually one of the three core languages of the web, alongside HTML and CSS. With JavaScript, you can target elements on the web page, listen to and trigger events, and complete pretty much anything else you’d like to accomplish within the bounds of client-side web interactions.

Think of interactions you’d like to happen in the web application’s page without it reloading, and that’s likely JavaScript. For example, if the user clicks a button and the page changes without having to take the time to reload.

Key Differences Between PHP vs. JavaScript

There are numerous differences between PHP vs. JavaScript, ranging from overall language type and execution, to popular use cases. In the table below, we walk through many of those key differences (keeping in mind that we're ignoring back-end use cases where JavaScript can be used) for a quick-reference comparison of PHP vs. JavaScript.

PHP vs. JavaScript Security

Security must be kept in mind no matter what language you’re using. PHP vs. JavaScript are no exceptions. Since PHP is server-side, most of it is secured through file permissions, making the core system private. Still, you must keep up-to-date with PHP versions and patches while also staying current with any frameworks or third-party packages you’re using to ensure all vulnerabilities have been patched and therefore secured.

In contrast, JavaScript is run client-side, and the user of the application has access to all the source code and data being used within, even if they’re minified and encrypted. This must be kept in mind while developing in JavaScript. Anything you don’t want the user to have access to read or modify must be kept out of the JavaScript of your application. Beyond that, you still need to stay current with any JavaScript frameworks or third-party packages to ensure any vulnerabilities are patched.

Speed

When comparing PHP vs. JavaScript, you'll find both are relatively performant, efficient, and snappy languages when it comes to their interpreters. PHP has especially had a multitude of performance increases since version 7 with a 2x performance increase, and performance has been a focus in each subsequent version since.

The difference between PHP vs. JavaScript speed lies in what the basis of their performance is. PHP’s performance is based upon the server’s configuration, while JavaScript’s is based on the client’s. In other words, you have a lot of control when it comes to the performance of your PHP. You can configure the server to be more performant or even throw more hardware at the problem. However, you have very little control on the end-user’s computer and its performance. 

It’s important to keep the lowest-denominator end-user in mind while writing your JavaScript and making sure they’ll have a reasonably snappy experience.

Syntax

PHP and JavaScript are very similar in syntax. They both have a syntax based on C. Some may say one is simpler than the other, but they’re both very simple syntaxes that are great for beginner level developers to learn. One key difference would be that PHP is procedural and synchronous by default unless modified with extensions and frameworks while JavaScript has asynchronous methodologies built in. There are some cosmetic differences as well as different features in both. Community standards are a bit different for both. They both have the same core feel, though, and a developer shouldn’t have much of a problem switching between the two.

PHP vs. JavaScript for Web Applications

PHP and JavaScript represent two of the most popular languages used in web applications, with PHP serving as the most popular choice for web back-ends, and JavaScript as the most popular for web front-ends. Let's walk through common use cases for both.

Common PHP Web Development Use Cases

PHP has a number of common web development use cases that range from form handling, data processing, and session management to authentication and content management systems.

Form Handling and Data Processing

It’s normally recommended as a best practice to do form handling and data processing on both ends of the pipeline for a more user friendly experience. For example, JavaScript can handle simple form and data validation without ever sending it off to the server, saving the user time by checking upfront. Whether you do both or not, PHP should always validate the form and process the data at the end, since users can spoof the JavaScript and payload to circumvent client-side validation.

PHP, being geared toward web development, is great at form handling and data processing. It has simple super globals ($_GET, $_POST, $_PUT, etc.) for handling form submittals and a vast amount of built in functions (trim(), substr(), str_replace(), etc.) as well as numerous database integrations for processing data.

Session Management and Authentication

PHP has built-in session management to make creating stateful applications simple, and many frameworks extend this built-in feature to be even more simple and feature rich. The session differs from cookies in that it is stored server-side, so it’s a better place to store sensitive data during a user’s session in the web application. You should still be careful of what you store there and study any vulnerabilities sessions may innately have.

Basic HTTP authentication can easily be written in PHP by utilizing the built-in super globals like $_SERVER[‘PHP_AUTH_USER’] and $_SERVER[‘PHP_AUTH_PW’]. Most frameworks will have some way of integrating with other authentication services, like OAuth and LDAP.

Content Management Systems

Due to PHP being one of the most popular server-side languages for Web Development, it has been adopted by many CMS communities. WordPress, Concrete CMS, October CMS, and many others are built using PHP. This may seem like a mundane choice, but keep in mind PHP’s simplicity. Due to its simple syntax and forgiving nature, PHP allows users of these content management systems to extend them and build their own modules for them with relative ease.

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Common JavaScript Web Development Use Cases

Like PHP, JavaScript has several common web development use cases, including AJAX, front-end frameworks, browser manipulation, DOM interaction, event handling, and user interaction.

AJAX

AJAX originally stands for Asynchronous JavaScript and XML, but it has evolved to become the term used for any programmatic technique where client-side creates asynchronous requests. For example, client-side sending an AJAX request to a web API to grab a list of products and display them.

Front-End Frameworks / Libraries

There’s a vast amount of front-end frameworks and libraries out there. From bulky and heavy to lightweight and agile, there’s a framework out there for your preferences, and it really does come down to personal preference. A couple of the big players are Angular and Vue.js. They all have their dogma and community standards. They can all get you from a to b, it just depends on the journey you’d like to take.

Angular, backed by Google, has leaned heavily into Typescript. Due to this, the code could be considered cleaner and more elegant. While you can write it however you like, the community standards are sometimes touted as strict and increase the learning curve. With two-way binding and verbose documentation concerning standards, you’ll end up with a powerful and clean code base when using Angular.

Vue.js is thought to be much more forgiving. You can use JavaScript or Typescript. There’s still two-way binding and a myriad of extensions. Vue’s learning curve is much less steep. It’s a great place to get started with a fully featured front-end framework.

At the end of the day, it’s worth it to take a little time, maybe a few weeks, just to toy around with a few frameworks to see which spark your interest and fit your need the most.

Browser Manipulation and DOM Interaction

This is where JavaScript shines, because this is the entire reason it was created. Imagine a world wide web with only HTML and CSS. No dynamic pages, no user interactions on the page. A page loads, you click a link, and a new page loads. Everything would be pretty boring.

With JavaScript, you’re able to target elements on the page and manipulate them. You’re able to dynamically change the HTML, and it changes for the user immediately. You’re able to quickly serve static information upfront in a matter of milliseconds, then fill it in as data loads through JavaScript, creating a snappier experience for the user. All those interactions that make the web more convenient and fun to use are due to JavaScript.

Event Handling and User Interaction

Due to JavaScript relying heavily on user interaction, it’s typically written in an event-driven fashion. While you can and will probably write procedural JavaScript, a majority of advanced web application JavaScript is driven by events. For example, when the user clicks a certain button, perhaps an event is triggered. In JavaScript, you can target that button, write a listener for it that waits for it to be clicked, and does something when that click happens. Maybe when that click happens, the listener runs a function to grab information about a single product and display it. This would be an example of event handling a user interaction.

Final Thoughts

As discussed above, PHP and JavaScript aren't the 1:1 comparison some make it out to be. It is less about PHP vs. JavaScript, and more about PHP and JavaScript. Both can be, and are, used as the front-end and back-end foundations of modern, scalable web applications. 

Of course, that clear front-end / back-end dichotomy is messier in reality, with JavaScript (via NodeJS) able to work in back-end use cases. While we didn't get into that part of the comparison today, keep an eye out for future content that compares NodeJS (and JavaScript) on back-end use cases.

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Additional Resources

• Resource Collection - Exploring PHP Versions
• Blog - PHP vs. Ruby vs. Ruby on Rails for Modern Web Apps
• Blog - When to Rewrite vs. Refactor Your Web App
• Blog - PHP vs. Python
• Blog - What Is PHP?
• Blog - PHP vs. Node.js: What's Best for Your Web App?
• Blog - PHP vs. Java: Which Is Right for Your App?
• Blog - How To Use PHP and ReactJS To Build Modern Web Apps
• Free Training Course - Installing PHP
• Free Training Course - PHP Basics
• Free Training Course - Interactive Web Forms