Meta box checkbox won't save

Question

I have several fields mostly text inputs to save additional info to the posts, all the text boxes save but i cant't get the checkbox to save the value!

Wondered whether any of you geniuses out there could help me. Thanks in advance.

The checkbox is below, which I echo the ck_sale in the checkbox input

$ck_sale = get_post_meta($post->ID, 'ck_sale_item', true); ?>

<?php //Save the information in the metabox
add_action( 'save_post', 'mb_product_details_save');
function mb_product_details_save( $post_id ) {
     // Bail if we're doing an auto save
    if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
        return;  
    }
    // if our nonce isn't there, or we can't verify it, bail
    if( !isset( $_POST['product_details_nonce'] ) || !wp_verify_nonce( $_POST['product_details_nonce'], 'mb_product_details_nonce' ) ) {
        return;    
    }
    // if our current user can't edit this post, bail
    if( !current_user_can( 'edit_post' ) ) {
        return;
    }

    //Set the data in the fields before saving
    if( isset( $_POST['tb_RRP_price'] ) ) {
        update_post_meta( $post_id, 'tb_RRP_price', wp_kses($_POST['tb_RRP_price']));
    }
     if( isset( $_POST['tb_trade_price'] ) ) {
        update_post_meta( $post_id, 'tb_trade_price', wp_kses($_POST['tb_trade_price']));
    }
     if( isset( $_POST['tb_colours'] ) ) {
        update_post_meta( $post_id, 'tb_colours', wp_kses($_POST['tb_colours']));
    }
     if( isset( $_POST['tb_quantity'] ) ) {
        update_post_meta( $post_id, 'tb_quantity', wp_kses($_POST['tb_quantity']));
    }

    if($_POST["ck_sale_item"] == "on") {
        $featured = "on";
    }
    else {
        $featured = "off";
    }
    update_post_meta($post->ID, 'ck_sale_item', $featured);
} ?>

Answer 1

I found the answer now it was the way i was trying to save it this is what I done in the save function

    if( isset( $_POST[ 'ck_sale_item' ] ) ) {
    update_post_meta( $post_id, 'ck_sale_item', 'on' );
} else {
    update_post_meta( $post_id, 'ck_sale_item', 'off' );
}