Splitting the cart by quantity

split_by_quantity.php

function custom_split_shipping_packages_shipping_class( $packages ) {

	// Reset all packages
	$packages              	= array();
	$split_package_qty 	= array();

	foreach ( WC()->cart->get_cart() as $item_key => $item ) {
		
		for( $i = 0; $i < $item['quantity']; $i++ ){

			$new_item 		= $item;
			$new_item['quantity'] 	= 1;

			$item_arr = array(
				$item_key => $new_item
			);
			$split_package_qty[] = $item_arr;
		}

	}
	
	for( $i = 0; $i < count( $split_package_qty ); $i++ ){
		$item_arr = $split_package_qty[$i];
		
		$packages[] = array(
			'contents'        => $item_arr,
			'contents_cost'   => array_sum( wp_list_pluck( $item_arr, 'line_total' ) ),
			'applied_coupons' => WC()->cart->get_applied_coupons(),
			'user'            => array(
				 'ID' => get_current_user_id(),
			),
			'destination'    => array(
				'country'    => WC()->customer->get_shipping_country(),
				'state'      => WC()->customer->get_shipping_state(),
				'postcode'   => WC()->customer->get_shipping_postcode(),
				'city'       => WC()->customer->get_shipping_city(),
				'address'    => WC()->customer->get_shipping_address(),
				'address_2'  => WC()->customer->get_shipping_address_2()
			)
		);
	}

	return $packages;

}
add_filter( 'woocommerce_cart_shipping_packages', 'custom_split_shipping_packages_shipping_class' );