Some doubts about how WordPress loop deeply work (trying to debug it)

Question

I am very new in WordPress development (and also in PHP development, I came from Java and C#). Today I have installed Aptana and configured XDebug to inspect what happens into the TwentyTwelve theme.

In particular I am trying to understand how WordPress load the posts by the loop (debbuging it).

So, since now, I only know how create a loop in a WP theme but I don't know how exactly it work.

So, in the TwentyTwelve I find the post loop, this code snippet:

From what I can understand the loop is composed by a while cycle where the have_posts() result is the condition to execute the while body.

Ok, now probabily the following question is related to my ignorance in PHP but what exactly means the construct:

<?php while ( have_posts() ) : the_post(); ?>

have_posts() is the condition to execute in the while but what exatly means the : the_post();

Is the_post() call the first operation of the cycle or what?

Then I have put a breackpoint into the have_posts() function definied into the query.php file.

function have_posts() {
    global $wp_query;

    return $wp_query->have_posts();
}

What exatly is the query.php file? Is it a class or what? Looking its code seems to me that it is not a class...why?

And what exactly represent $wp_query variable? Is it an object or what? (PHP is not typed so how can I know what a variable contains?)

What means this operation:

$wp_query->have_posts();

I think that it call another version of the have_posts() function (definied into the query.php file) that check if exist some other post to show or if they are ended.

But how exactly work? Reading the PHP OO documentation the -> operator call a method of an object but I don't know if $wp_query is an object or if in this contes the -> operator have another sense...

Can you help me to understand how exactly it work?

Tnx

If you are new to PHP may I introduce you your new best friend var_dump. — Tomás Cot

vico vico · Accepted Answer · 2014-08-05T20:15:51

To understand how loop works in wordpress you will have to understand some basics in php

before the function <?php while ( have_posts() ) : the_post(); ?> there is a global query of arrays that is in the wordpress post array format [0][1][2][3]

so while have post the post just means, if there is a post, that element is set to THE POST

it sets all calls to relay to contents in that single array http://codex.wordpress.org/Function_Reference/the_post

for example when you call the_content() you are displaying that post's index and inside there there is a 'content' => 'contents goes here'

long story short, learn the wordpress predefined syntax and how loop works on their documentation site.

located here http://codex.wordpress.org/Function_Reference/

Some doubts about how WordPress loop deeply work (trying to debug it)

1 Answers