[Plugin: Smarter Navigation] How to link prev/next post in parent category?

Hi. At this point (7 months later) I don’t remember really well but I think that I did it. Finally I decided to use another way to show my posts so I didn’t need this function anymore.

First, download and install this plugin:
Ambrosite Next/Previous Post Link Plus

Second, you need to know where you are coming from (home / category archive). To get this goal I decided to use sessions.

1) At functions.php you need to enable sessions to work. Put this code at the beggining of the file:

/**
 *    init_sessions()
 *
 *    @uses session_id()
 *    @uses session_start()
 */
function init_sessions() {
    if (!session_id()) {
        session_start();
    }
}
add_action('init', 'init_sessions');

2) Enable “history” (where you are coming from?). Put this code in footer.php before <?php wp_footer(); ?>

$this_category = get_category($cat) // get category ID;
if (is_home()) {
$_SESSION['history'] =  "home";
} else if (is_category('portfolio')) {
$_SESSION['history'] =  "portfolio";
} else if ($this_category->category_parent == 1) { // for "portfolio" child categories
$_SESSION['history'] =  "portfolio subcategory";
}

Now you have sessions working, you need to use conditional tags in single.php.

if(isset($_SESSION['history'])){ // if "history" session exists
if ($_SESSION['history'] == "home" || $_SESSION['history'] == "portfolio") { // if you come from home or portfolio, use prev/next links plus code
previous_post_link_plus(array('format' => '<span class="prev">%link</span>', 'link' => '« PREV', 'ex_cats' => '9'));
next_post_link_plus(array('format' => '<span class="prev">%link</span>', 'link' => 'NEXT »', 'ex_cats' => '9'));
} else if ($_SESSION['history'] == "subcategoria portfolio") { // if you come from a portfolio subcategory use native wordpress prev / next links
previous_post_link ('<span class="next">%link</span>','« PREV', TRUE);
next_post_link ('<span class="prev">%link</span>','NEXT »', TRUE);
}
} else { // if "history" doesn't exist use prev/next links plus code (maybe this code is not necessary)
previous_post_link_plus(array('format' => '<span class="prev">%link</span>', 'link' => '« PREV', 'ex_cats' => '9'));
next_post_link_plus(array('format' => '<span class="prev">%link</span>', 'link' => 'NEXT »', 'ex_cats' => '9'));
}

Well, like I said, I don’t remember really well if this worked ok (I think I get it but I’m not sure). Let me know if this works for you.

ps: sorry for my english.

Ok. The blank problem maybe is because of a bad closed code. Check if nothing is missing. Try one step at once to check in wich step you get the blank page. Perhaps I forget to close a conditional statement.

Mmmm… How are you managin your post? When you publish a post you check both parent and child category or only the child category?

In my example the “portfolio” session history have this name because I want to know if visitor comes from “portfolio” category. In your case, you can replace it by your own category.

In my case, this parameter ‘ex_cats’ => ‘9’ excludes the category “news” so I cant navigate through post in any portfolio posts (asigned to a portfolio subcategory).

In the default linking navigation the parameter TRUE tells navigation that you want to navigate between posts in same category.

So, to be clear:

If I came from home or portfolio (I display posts that belongs the portfolio subcategories in home page) > Allow posts navigation between posts in ANY portfolio subcategory.

If I came from a portfolio subcategory, navigate through posts in same subcategory.
edit: I notice that when I translated my code I left a piece of spanish code, so in your theme code in footer you have to replace
} else if ($_SESSION[‘history’] == “subcategoria portfolio”) {
with
} else if ($_SESSION[‘history’] == “portfolio subcategory”) {

By “enable history” I want to mean that you have to declare the session. In my case I call it “history”.

I hope to be clearer.

ps: once again, sorry for my “tarzan english”.

No problem, you’re welcome!

Tell me what’s the problem.

I always hide the bar (in frontpage) via functions.php but that’s not the case.

Does your code in footer.php looks similar to this?

<?php
$this_category = get_category($cat);
if (is_home() || is_front_page()) {
$_SESSION['history'] =  "home";
} else if (is_category('portfolio')) {
$_SESSION['history'] =  "portfolio";
} else if ($this_category->category_parent == 1) {
$_SESSION['history'] =  "portfolio subcategory";
}
?>
<?php wp_footer(); ?>

Note: you have to change “is_category(‘portfolio’)” with your category slug and $this_category->category_parent == 1 with the ID of that category (in my case “portfolio” category ID = 1).

php tags is correct.

I’m assuming you know about php code. Do you?