Some WordPress multisite useful coding

WordPress multi-site (WP MU) has some useful functions and the one for determining the blogs count is:

$blog_count = get_blog_count();

You would probable have the alternative to get the blog count with this function :

$blog_ids=array();
$blog_list = get_blog_list( 0, 'all' );
$blog_count = count($blog_list);

Also when having the blog list you can have the blog IDs easily…

foreach ($blog_list AS $blog) {
  $blog_ids[] = $blog[blog_id];
}

In WP MU you will often have to write custom queries so you can use your blog count for this… and often time you can create UNION and not execute a single query for every instance… like this

for($c = 1; $c>= $blog_count; $c++){
$prefix = $wpdb->get_blog_prefix($id);
$sqlarr[] = "SELECT `meta_value` FROM `{$prefix}postmeta` WHERE `meta_key`='location'";
$ret = $wpdb->query($sql);
}
$sql = implode(" UNION ", $sqlarr);
$ret = $wpdb->get_col($sql);

Use

switch_to_blog($blogid);

when you need for instance to get post metadata but for some specific blog:

$cost = get_post_meta( $post_id, "cost", true );

…

tags: & category: -