According to Wikipedia, “PHP is a server-side scripting language”. What the heck does that mean?

Server-side – a server is just a type of computer, like your phone or laptop – with a specific purpose – like your phone or laptop. Server-side means that all the work in creating the web page created in PHP is done on the server. The client (server/client relationship) is your computer/device that just displays the resulting HTML, CSS, and javascript.

Scripting – the code is not complied into machine language – it remains human-readable

Language – a set of instructions (and rules) to make computers do what we want them to do. Every time, even when they break. 🙂

Some solid advice, adapted from Presscoders.com.

1. See if a theme option will do the trick first

2. Use CSS to manipulate design (child theme style.css file)

3. Use functions.php for structural changes

4. Add new template files to a child theme

5. Use a plugin (only for major feature additions)

Use your staging environment and make a backup before you do anything!

First, FTP or otherwise access your we server. Create a new document and call it “neat.php”. PHP files are just text files so you should be able to open the file in your text editor of choice.

Copy the following to your “neat.php”, save the file, and then open the file in your web browser. http://yoursitename.com/neat.php

You should now see the words “Hello world” in your browser.

The  text you copied over is PHP! The first line let’s the server know the following text should be treated as PHP code. The second is our code. “echo” is a PHP command that outputs the strings (the text) it is being passed as arguments. So we’re saying, “Hey PHP, output the following bit of text. The colon is an instruction separator. We’re telling PHP that we’re done with this instruction. The last sentence tells the server, We’re done running PHP. You can stop now.

Here’s some PHP inside of an HTML element.

This is our same PHP code as before, but this time its inside of an HTML div. As you can see in this very simple example, your HTML and PHP can live inside of one another. Having HTML inside of PHP is a little more complicated to explain, but also possible.

WordPress uses PHP across the software. Most commonly for most WordPress users you’ll find it inside of your Theme files. These files are called templates.

Using your text editor, open the “footer.php” file in your theme of choice. Each theme’s file will look differently, but you can see that the code inside the template defines what the footer (bottom most section of your pages) will look like.

Some themes are broken up into even smaller units like for instance:

“template-parts/footer/site-info.php”

Everything!

Small little changes like we did above in our child theme. The best way to learn when starting out is to just go muck with something, save the file and see what happens. If something breaks or doesn’t behave like you expect, undo your changes, save, and try again.

The loop is the way WordPress builds individual posts. You an modify things inside the loop so it applies to every post that appears – either by itself or in a list like say your blog or a category.

functions.php

One way to modify your WordPress site is by editing your theme’s functions.php !

Here’s an example that allows you to customize the login form users see when administering a site.

You can hack an existing theme, or create your own. Instead of starting from scratch, use a starter theme!

As an aside: Starter themes are really basic themes that provide a base for you to build your own custom themes without starting totally from scratch. They often contain little to no styling.

A popular example:  http://underscores.me

Let’s mess around a little with our footer.php. What happens if you add each of these lines to your code? Where does it break or not work?

More on WordPress functions:

Since PHPis a scripting language and not compiled, we can view and modify any of the code we see in WordPress – including plugins!

One of the most simple and popular plugins that you can look at to see how it works:

You can also use PHP to store, retrieve, and modify content from the database! WordPress stuff, or you can extend it to your own schema!

One of my favorite is Advanced Custom Fields – gives you control over how content is entered, and then uses short PHP snippets to include in your theme files.

Debugging errors in WordPress/PHP is something you’ll have to run into when working with your site. A few resources:

Google! Just enter the most generic parts of the error message with the word “WordPress: will lead to discussion (and hopefully answers) where other people have encountered similar issues.