The loop that we looked at in the last video is highly customizable

using something called WP_Query.

For example, when you're working with custom post types or

custom themes, you'll often see WP_Query in use.

And it's super helpful to understand how it works and

see how to customize it a bit.

Let's start off looking at the codex documentation for WP_Query and

find out different ways that we can customize the loop.

Then we'll look at WP_Query in action, and

see how we might want to use it to customize a theme.

There's a great page on the WP codex on WP_Query.

It starts off with talking about what WP_Query does, and

showing the standard loop and a few alternative ways of doing it.

It then goes through and

it shows all of the different types of parameters that you could use to customize

what you want that loop to display and what conditions it should meet.

For example, there are author parameters, if you just want to display things from

certain categories Whether you want to display certain post or page parameters,

status parameters, custom field parameters and a lot of other ones.

We'll scroll through briefly just to get an idea of some of what's available.

However, it's good that you come back on your own and

look at this in more depth to get an idea of what's really possible.

We see here that we can choose author names or author IDs.

Certain categories.

Certain tags, taxonomy parameters.

You could even include a search parameter, a specific page post slug or post ID.

Whether or not it has a password set, what post types are available.

And we'll pause real quick here to look at the template in action, and

then we'll come back and look at a few more of these.

What I did on my site was I set up a custom page and

by the Template option I chose Custom Template.

I also went under Widgets.

And made sure that I had a Pages widget so

that I can navigate around my site a little bit.

I could then come to my custom page and

I could see that it's outputting three different blog posts.

These are the three posts that I have saved as posts in the admin area.

If we come into our theme folder now and we open up page-custom.php,

we could see up top here that I named the Template Name Custom Template.

This is how WordPress knows that we're dealing with a custom template.

And then down here,

I started a new WP_Query preceded by the arguments I wanted to set.

So we have the arguments, the call to a new WP_Query, and then we have our loop

customized to have_posts to check if there's posts for this new query.

And then while there are results of this new query,

echo them out inside of a list item.

And we're not doing anything if there's nothing found.

One important thing about working with WP_Query,

especially when you use multiple queries on one page, is that you want to reset

the post data afterwards in case there are other loops that it may interfere with.

So what we have here is post_type post.

And on our site we can see that it's displaying posts.

If we change this to post_type page,

we should see that on our site we're now echoing out a list of pages.

At this point we only have one, but

if we added more we'd see more of them linked here.

We can come back to post.

And then let's come back into our WP_Query page on the WP codex, and

look at a few more customizations that we can make.

It's also important to note that if you have custom post_types,

such as an events or portfolio one,

this is the call that you would make in order to display custom post_types.

We could then see that we could customize by post_status, pagination

parameters, and a very important one that we have here is posts_per_page.

This is what we would use to set how many posts we want to display.

So if we want to add another parameter we would put a comma,

posts_per_page, and then the number 1, for example.

And now when we test our page we would see that there's only one displaying.

We could also customize the order that these are displaying.

So we could see order ascending and descending.

Let's try changing this.

Now a quick note about what I did.

You could see when I wrote a number, I didn't have to put it inside of quotes

because PHP can handle numbers on their own.

However, if I want to write out some characters, what's referred to as a string

in WordPress, I have to wrap it inside of parentheses, single or double.

Again, this is something you would pick up more when you study PHP on its own.

But I just want to mention that here because you will see when you're working

with custom post_types that if the value is just going to be a number,

you don't put it inside of quotes.

But if it is a text value or string, then you do have to put it inside of quotes.

So now if we come back and we refresh, we can see we have Hello world, Universe,

Treehouse.

And if we try descending, we have a different order.

We could also change the order by which they appear, for example,

by ID, by title, by post name.

So let's try adding one of these in.

And let's do by title.

And we could see we have w first.

If we were to change that to ascending, then we would see that change.

We could also output random orders or

by parent as well as a whole lot of other options.

But determining what order you want things to appear is pretty common.

And you can see it has examples here of popular posts by orderby

the number of comment_count.

If you have prices as a custom value you could

do a customized output here of how you want them to appear by price.

And then we can have date parameters.

For example, let's say that we just wanted to have something that appears

on a specific date.

We could do that a certain way, for example, setting the year, month and day.

And we're seeing this written as an array with an and

sign in between because this value is going directly here.

However, this is a more common way of writing them out, and you would simply

take each one of these and put them on their own line in this fashion,

separating them by commas and leaving off the comma in the last one.

Again, writing arrays is something you would study in more depth as you study

PHP on its own.

However, we'll point it out here because it's something pretty common you

need to know when working with WP_Query.

So this list goes on and on, even allowing you to search by custom fields, and

doing quite a lot to customize how your content is outputted.

We'll stop here for now.

However, I encourage you to continue to look at these in depth so

that you can get an idea of what is possible when working with WP_Query.