hijiriworld/intuitive-custom-post-order -- Scrap existing menu_order values after reordering.

intuitive-custom-post-order.php

// Fixes duplicate items showing up if the same menu_order is shared between two items across a page break.
// Replace update_menu_order() with the code below.

	function update_menu_order()
	{
		global $wpdb;

		parse_str( $_POST['order'], $data );

		if ( !is_array( $data ) ) return false;
			
		// get objects per now page
		$id_arr = array();
		foreach( $data as $key => $values ) {
			foreach( $values as $position => $id ) {
				$id_arr[] = $id;
			}
		}

		// get menu_order of objects per now page
		$menu_order_arr = array();
		foreach( $id_arr as $key => $id ) {
			$results = $wpdb->get_results( "SELECT menu_order FROM $wpdb->posts WHERE ID = ".intval( $id ) );
			foreach( $results as $result ) {
				$menu_order_arr[] = $result->menu_order;
			}
		}
		
		// maintains key association = no
		sort( $menu_order_arr );
		
		// Orangepineapple.com -- Scrap old $menu_order_arr; use the min value as a starting point for new menu_order.
		$first_post = min($menu_order_arr);

		foreach( $data as $key => $values ) {
			foreach( $values as $position => $id ) {
				// Orangepineapple.com -- Scrap old $menu_order_arr; use the min value as a starting point for new menu_order.
				// $wpdb->update( $wpdb->posts, array( 'menu_order' => $menu_order_arr[$position] ), array( 'ID' => intval( $id ) ) );
				$post_order = $first_post + $position;
				$wpdb->update( $wpdb->posts, array( 'menu_order' => $post_order ), array( 'ID' => intval( $id ) ) );
			}
		}
	}

Fixes duplicate items showing up if the same menu_order is shared between two items across a queried page break.