[PATH] Clear cache button

I noticed there’s no clear cache button. This can be an issue for example when you change the date or add new posts that should relate to a previous one.

As an example if you have Post X that has a Post Y in its related post list then change the date on Post Y, the URL on the cached post list on the Post X page won’t update accordingly and it’ll lead to a 404.
Another example is if you create Post X and it has no related posts. If you then create Post Y and want it to relate to X, you probably want Y to appear in X’s related post list. A clear cache button is required to do this so next page load a new related post list is generated.

I added a simple ‘Clear Cache’ button to the admin like so. In admin.inc.php below

<p class="description"><?php _e('Enabling this option will cache the related posts output when the post is visited the first time. The cache is cleaned when you save this page.',CRP_LOCAL_NAME); ?></p>

add

<p><input type="button" value="<?php _e('Clear cache',CRP_LOCAL_NAME) ?>" onclick="return clearCache();" /></p>

and above

function checkForm() {

in the JS at the bottom of the file add

function clearCache() {
	// since 2.8 ajaxurl is always defined in the admin header and points to admin-ajax.php
	jQuery.post(ajaxurl, {action: 'crp_clear_cache'}, function(response, textStatus, jqXHR) {
		alert( response.message );
	}, 'json');
}

That’s the HTML taken care of, now for the actual logic to delete the cache. In contextual-related-posts.php at the bottom above

// End admin.inc

add

add_action('wp_ajax_crp_clear_cache', 'crp_ajax_clearcache');
function crp_ajax_clearcache() {
	global $wpdb; // this is how you get access to the database

	$rows = $wpdb->query("
		DELETE FROM " . $wpdb->postmeta . "
		WHERE meta_key='crp_related_posts'
	");

	// Did an error occur?
	if ( $rows === false )
		exit(json_encode(array(
			'success' => 0,
			'message' => "An error occurred clearing the cache. Please contact your site administrator.\n\nError message:\n" . $wpdb->print_error(),
		)));
	// No error, return the number of
	else
		exit(json_encode(array(
			'success' => 1,
			'message' => $rows . " cached row(s) cleared.",
		)));
}

While I was in there I also fixed an error you get when updating settings with WP_DEBUG turned on:

Notice: Undefined index: post_types in /path/to/wp-content/plugins/contextual-related-posts/admin.inc.php on line 84

by changing

$post_types_arr = (is_array($_POST['post_types'])) ? $_POST['post_types'] : array('post' => 'post');

to

$post_types_arr = (isset($_POST['post_types']) && is_array($_POST['post_types'])) ? $_POST['post_types'] : array('post' => 'post');

http://ww.wp.xz.cn/extend/plugins/contextual-related-posts/