What is PHP and why does it matter?

What is PHP, and how does it impact your blog?

For most of my 10-year blogging career, the only thing I knew about PHP was that breaking it instantly took my entire site offline, replacing both the front and back ends with a blank white page. I would occasionally add or update PHP code to customize my theme or add new functionality, but for the most part, I tried to stay as far away from it as possible. (And thankfully Peter and Morgan were always there to bail me out when I did mess it up.)

Thankfully, you don’t need to become fluent in PHP to be a successful blogger. But we strongly believe that having a basic understanding of the technical details that impact your site is an important foundation for growing your business. Because it plays such a key role in WordPress (and much of the internet), let’s take a look at PHP and what it does:

What is PHP?

PHP is a server-side programming language. In plain English, it’s used to perform the tasks that make your site run the way it does, before it ever gets to your visitors’ browsers. In other words, PHP makes your site function. In fact, the PHP file found in most WordPress theme packages is even named functions.php.

Think of it like the electrical wiring in your home. When you flip a light switch, you don’t actually see what’s happening in the walls, but the wiring makes everything work the way you (or your electrician 🙂) want it to.

WordPress itself is written in PHP, making it an essential part of your site’s architecture and controlling how all of the different pieces of your theme and plugins work together. Using the home wiring analogy, when you flip a certain light switch, you’re probably not even thinking about the electricity itself. All that matters to you is the light, or the output. On your site, this output is a mixture of HTML, JavaScript & CSS. But the wiring behind the scenes (i.e. PHP) is what makes the lightbulb work.

Does PHP change?

All programming languages change over time. As they change, different features and commands are deprecated, meaning they are phased out slowly and replaced with better alternatives. For example, many HTML attributes (including align and size) have been deprecated as best practice has moved toward using CSS for this formatting instead.

PHP is no different, and new major versions are released, on average, every year. Once a new version is released, bugs and security issues are addressed for 2 to 3 years. After that time, a version may still function properly, but it will no longer be supported, which means it won’t be the fastest, and it could even be insecure. The PHP website provides a list of all supported versions, as well as their planned lifecycles.

Unlike other programming languages—such as HTML and JavaScript—where you simply write the code and the end user’s browser interprets it, PHP has to be installed on your server in order to run. When HTML, CSS, or other programming languages are updated, you can simply begin using the new code, and it will work. Of course, users who have an older browser may see something completely different than you intended, which is why designers and developers should test their work across a wide variety of devices and browsers. But the there’s nothing else you need to install as a blogger before you begin using that code.

On the other hand, because PHP runs from your server, the PHP package on your server has to be updated in order to switch from an older version to a new one. This is a manual process, and the exact process looks different depending on your hosting company. For Agathon clients, it only takes 30 seconds to update (seriously, I just timed it!). Keep reading for those instructions. But first…

What happens if I don’t update PHP?

Because PHP versions are only supported for about 3 years, PHP 7.0 has already reached its end of life (EOL), and PHP 7.1 is just a few months away. Unsupported versions can have security vulnerabilities, so it’s important to upgrade to keep your site secure.

In addition, WordPress has announced that the minimum PHP version required to run WordPress is now 5.6, and that’s expected to jump to 7.0 by the end of the year. Beyond that, the improvements to PHP 7.3 could mean a significant increase in your site speed.

Updating PHP

How do I know which version of PHP my site uses? How do I know if I need to upgrade PHP?

To check the PHP version on your site, log into your WordPress admin dashboard and go to ToolsSite HealthServerPHP version.

To upgrade PHP on your server

Note: These instructions are for customers hosted with Agathon. If you’re not hosted with us, ask your current host how to upgrade to the latest version of PHP.

  1. Log into Virtualmin (if you don’t have these details handy, check your Agathon welcome email or email support). 
  2. If you have multiple sites hosted, choose the site you’d like to upgrade from the dropdown at the top of the left sidebar.
  3. On the left sidebar, click Server Configuration and then PHP Versions.
  4. Click on the dropdown menu next to Default HTML directory and select the most recent version of PHP (the last one on the list).
  5. Click Save Versions.
  6. You should see a confirmation message: “The virtual server NAME has been successfully updated. Use the links below to continue managing it.”
  7. Repeat for each site on your server.
  8. Make sure everything looks right on your site. If something isn’t working right, simply perform the same steps above to switch back to the old version and email support so we can take a look.

Note: You’ll see a second blank directory with a default PHP version. You should not change any of these settings unless you know what you’re doing; most sites will not use separate directories.

If I have multiple sites on my server, will I need to upgrade each one?

Yes. The PHP version is set for each site, so you’ll need to repeat the process for each one. To do that, select each site one by one from the dropdown menu at the top of the left sidebar.

Can you do this for me?

Updating the PHP version is very straightforward, and we’re confident you can do it easily following the steps above. But if you need help, email us at support@agathongroup.com and we’d be happy to help.

Can updating PHP break my site?

If your site is already running on PHP 7, and you’re upgrading from 7.0.x-7.2.x to 7.3, the update will probably go smoothly without any noticeable difference on your site other than better site performance. There are rare instances where the newer version could cause problems; those are less likely if your plugins and WordPress version are up to date before you make the switch.

If you’re using PHP 5.6 or earlier, it’s possible that upgrading to PHP 7 could break your site in small (or in some cases, large) ways.

The good news is if you see something wonky after updating, you can simply revert back to the older version of PHP while you make plans for fixing that feature. (As always, feel free to contact client support if you need help!)

How will I know when the next version of PHP is released?

Our team has been hard at work creating a notification process for clients that will provide specific details on your current version of PHP and whether you need to update. Starting this week, we’ll be sending out emails letting you know when a new version of PHP is available on your server so you can be sure your site is using the latest stable version.


PHP may not be something you need to think about often, but hopefully this primer gives you a basic understanding of what it does and why those updates matter!

Mandi Ehman

Director of Marketing at Agathon
With 10 years of experience as a professional blogger—and as a former Agathon hosting client herself—Mandi’s passionate about the good work Agathon does and sharing that message with more people.
Mandi Ehman

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