Editor meta box Showing but not saving

Question

I am trying to create an editor meta box and I have been following tips found in other similar questions without luck in getting the meta box to save and display its content. The meta box shows but when I write anything it doesn't get saved. Please help! I've been at this for hours without any luck.

Here is my code at the moment:

add_action( 'add_meta_boxes', 'add_educadme_related_resources_metabox' );   
// Add the Custom Fields Meta Boxe
function add_educadme_related_resources_metabox() {

    add_meta_box('educadme_related_resources', 'معلومات إضافية', 'display_educadme_related_resources', 'lesson', 'normal', 'high');

}


// Display The Custom Fields Meta Metabox
function display_educadme_related_resources( $post ) {

    // Get the resources data if its already been entered
    $educadme_resources = get_post_meta($post->ID, 'related_resources', true);
    wp_editor( $educadme_resources, 'related_resources');

}

add_action( 'save_post', 'save_educadme_related_resources' );
// Save Function    
function save_educadme_related_resources( $post_id ){
    // Is the user allowed to edit the post or page?
    if ( !current_user_can( 'edit_post', $post_id ))
        return;
    // check autosave
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
        return;
    }
    // If empty don't do anything (don't save)
    $related_resources = get_post_meta($post_id, 'related_resources', true);
    if(!$related_resources OR $related_resources == '') return;

    // OK, authenticated: we need to find and save the data
    if ( isset ( $_POST['related_resources'] ) ) {
        update_post_meta( $post_id, 'related_resources', $_POST['related_resources'] );
    }

}

Answer 1

The problem was with this line:

 if(!$related_resources OR $related_resources == '') return;

I changed it to:

 if($related_resources == '') return;

And it started working properly. I hope others can make use of the code too. Thanks!