For example, you need to save list of users, who entered each page or post:
global $post, $current_user;
$data = unserialize(get_post_meta($post->ID, '_list', true));
if( count($data) != 0 ) {
if ( !in_array( $current_user->ID, $data ) ) {
$data[] = $current_user->ID;
}
$data = array_unique($data); // remove duplicates
sort( $data ); // sort array
//$data = serialize($data);
update_post_meta($post->ID, '_list', $data);
} else {
$data = array();
$data[0] = $current_user->ID;
//$data = serialize($data);
update_post_meta($post->ID, '_list', $data);
}
Great, this really helps!
It doesn't work with the latest WordPress however. This line in both blocks isn't necessary:
$data = serialize($data);
In fact it will store a serialized string containing the serialized array in it. WordPress automatically serializes arrays when update_post_meta is called.
Great! very helpfull... thanks!