In order to write PHP inside of a PHP file,

you have to do one more step then just saving the file with the extension .PHP.

You must also open and close what's called a PHP block.

You open and close a PHP block like this.

If you try to write PHP outside of a PHP block, it will display as plain text.

Likewise, if you try to write plain HTML inside of a PHP block,

it will cause an error.

In some files, like most core WordPress files,

you open the PHP block at the top of the file and close it at the end.

This means that you are writing exclusively PHP.

In other files like template files, you open and close

PHP blocks multiple times throughout the file whenever you want to write some PHP.

This means that you will likely have a combination of HTML and

PHP in the same file.

Both situations are perfectly acceptable in WordPress, and what you need to do in

any specific PHP file will determine what approach you take.

Let's take a look at a typical PHP only file.

We're going to go ahead and open the WP config file in our text editor.

We'll see that it opens with a PHP block, has a whole bunch of PHP.

But then, when we come down to the bottom, it does not close the PHP block.

This is an interesting thing in WordPress.

Technically, we could, and some say should, close this PHP block.

However, it will not break this to not close it.

And WordPress or the server running it will automatically close the block for us.

There are a couple of reasons that the WordPress developers do this.

One was they were concerned that if they didn't close the PHP block, and

someone tried to start coding PHP after this, that it could cause an error.

The other is that sometimes even just having extra white spaces

at the end of a PHP file outside of the closing block can cause problems.

For this reason, a lot of PHP

only files in WordPress do not have the closing end of the block added.

However, when you're coding your own files

generally you'll want to close the PHP block.

Let's take a look now at a file that contains quite a bit of HTML with only

a little bit of PHP inside of it.

We'll go ahead open up the 2015 default theme header file.

We could see that at the top of this header.php,

we have a PHP code block that opens here and ends here, with a comment inside,

a whole lot of HTML, and then little pieces of PHP that

are open and closed and only output a small amount of PHP.

This is fairly common.

We also see another type of PHP block, that we'll look at more later,

that's a conditional one that has some PHP, HTML inside of it,

some more PHP, more HTML, and back and forth like this.

We'll look at this shorthand of writing PHP a little bit later when we get to

the conditionals.

However, this template serves as a good example of a primarily

HTML file that simply has some PHP code blocks inside of it.

We'll look at one last file here, which is the functions.php.

This is one, again, that is primarily PHP, but

we may end up finding some HTML coded inside of it.

It depends on what that theme needs, and whether or

not they'll have HTML coded within it.

However, in this one, when we see our HTML coded, it's all appearing inside

of PHP itself, and they don't close and open the block to write it out.

Now that we've practiced opening and

closing some PHP files, let's take a look at what happens when we have an error,

specifically, one that involves the ever important semicolon.