pagination to next page with the same parent WordPress

jevusi comments:

i want display only the pages whiche have the same parent.

Ivaylo Draganov comments:

Yes, I understand your goal. I am currently working on that :)

Ivaylo Draganov comments:

I think I've cracked it. Put this in your <em>functions.php</em>:

// function to filter the where clause in the query for adjacent posts
function sql_get_adjacent_post_where( $previous = true ) {

global $post, $wpdb;

// set SQL comparison operator
$op = $previous ? '<' : '>';

// build and return where clause
return $wpdb->prepare("WHERE p.post_date {$op} %s AND p.post_type = %s AND p.post_status = 'publish' AND p.post_parent = %s", $post->post_date, $post->post_type, $post->post_parent);

}

// previoust post where clause
function sql_get_previous_post_where() {
return sql_get_adjacent_post_where();
}

// next post where clause
function sql_get_next_post_where() {
return sql_get_adjacent_post_where( false );
}


And the use this to print the links in your <em>page.php</em>:

// filter queries
add_filter( 'get_previous_post_where', 'sql_get_previous_post_where', $in_same_cat, $excluded_categories );
add_filter( 'get_next_post_where', 'sql_get_next_post_where', $in_same_cat, $excluded_categories );

// print links
adjacent_post_link('%link', '%title'); // preious page
adjacent_post_link('%link', '%title', false, '', false); // next page


Works for me with subpages of the main page. It could be wrapped in a single template function but I find that a bit overkill. Let me know if you manage to apply it.

jevusi comments:

Ivaylo, you use get_previous_post_where but here http://adambrown.info/p/wp_hooks/hook/get_previous_post_where i can see "Warning! This hook has been renamed!"
Is is not a problem ?

Ivaylo Draganov comments:

Yes, it is now a variable hook:
[[LINK href="http://mobile.adambrown.info/p/wp_hooks/hook/get_%7B$adjacent%7D_post_where"]]http://mobile.adambrown.info/p/wp_hooks/hook/get_%7B$adjacent%7D_post_where[[/LINK]]


get_{$adjacent}_post_where


It refers both to <em>get_next_post_where</em> and <em>get_previous_post_where</em>

I will try to see whether I can optimize that code down to a single function for applying the filters. But if you like, you can use it like that as well.

Ivaylo Draganov comments:

Seems like filters can't be applied inside of the same function, so you should use the code like it is. Just change the filters to avoid a PHP Notice for undefined variables:

add_filter( 'get_previous_post_where', 'sql_get_previous_post_where', false, '' );
add_filter( 'get_next_post_where', 'sql_get_next_post_where', false, '' );


I hope this is the result that you were after. Cheers :-)

Ivaylo Draganov comments:

You can change the way that links appear with by passing parameters to the function [[LINK href="http://hitchhackerguide.com/2011/02/11/adjacent_post_link/"]]adjacent_post_link[[/LINK]]. There's no codex page for it, but the parameters are the same as for [[LINK href="http://codex.wordpress.org/Function_Reference/next_post_link"]]next_post_link[[/LINK]].

For example this gives you a link with the page title as its text:

adjacent_post_link('%link', '%title');


And this will just read "Previous page":

adjacent_post_link('%link', 'Previous page');


Appending/prepending text is also possible:

adjacent_post_link('Previous page: %link', '%title');