Wordpress: issue on update_post_meta for checkbox metabox - wordpress

Question

I have a metabox (one checkbox) , in posts, to check if a post will be featured..
My code:
function add_featured_post_checkbox() {
add_meta_box(
'custom_featured_meta',
'Featured post for Sidebar',
'featured_post_checkbox_callback',
'Post',
'side',
'high'
);
} add_action( 'add_meta_boxes', 'add_featured_post_checkbox' );
Callback function:
function featured_post_checkbox_callback( $post ) {
wp_nonce_field( 'custom_save_data' , 'custom_featured_nonce' );
$featured = get_post_meta($post->ID, '_featured_post', true);
echo "<label for='_featured_post'>".__('Is Featured? ', 'foobar')."</label>";
echo "<input type='checkbox' name='_featured_post' id='featured_post' value='1' " . checked(1, $featured) . " />";
}
Save function:
function custom_save_data( $post_id ) {
if( ! isset( $_POST['custom_featured_nonce'] ) ){
return;
}
if( ! wp_verify_nonce( $_POST['custom_featured_nonce'], 'custom_save_data') ) {
return;
}
if( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ){
return;
}
if( ! current_user_can( 'edit_post', $post_id ) ) {
return;
}
if( ! isset( $_POST['_featured_post'] ) ) {
return;
}
$my_data_featured = sanitize_text_field( $_POST['_featured_post'] );
update_post_meta( $post_id, '_featured_post', $my_data_featured );
} add_action( 'save_post', 'custom_save_data' );
This code works well only when I want to make a post featured..
For example if a post is not checked as featured and I select the choice then database updated perfect (with value 1 in post_meta) and the ckeckbox has the tick on box
But after, If I try to uncheck and save the post then the ckeckbox is again with the tick and nothing changed in database..
I try to find a solution for days on stackoverflow and general in web but I can't find.
Please help me
Thank you

Answer 1

When a checkbox is unchecked, $_POST will not contain the key _featured_post. Therefore, in your save callback, you need to change your strategy. You do not want to bail out if the key is not set. Rather, you either want to save a 0 or delete the post meta. Let's go with the later option.
function custom_save_data( $post_id ) {
if( ! isset( $_POST['custom_featured_nonce'] ) ){
return;
}
if( ! wp_verify_nonce( $_POST['custom_featured_nonce'], 'custom_save_data') ) {
return;
}
if( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ){
return;
}
if( ! current_user_can( 'edit_post', $post_id ) ) {
return;
}
if ( isset( $_POST['_featured_post'] ) ) {
update_post_meta( $post_id, '_featured_post', 1 );
} else {
delete_post_meta( $post_id, '_featured_post' );
}
}
Notice that you do not need to use sanitize_text_field(). Why? Because the value will only be a 1. That's it. Here we can hardcode that value.
Another Problem I Saw
Running your code I saw that upon being checked, the HTML for checked=checked is being rendered as text. Why? Because running the function checked() will echo it out to the browser unless you tell it not to. You'd have to check your code to:
checked(1, $featured, false);

Answer 2

That's happening because of return after the check if _featured_post is set in $_POST array. It's not set when you do not check the checkbox. Your approach here should be next
if (isset($_POST['_featured_post']))
{
update_post_meta($object_id, '_featured_post', 1); // can only be 1 when checked anyway
}
else
{
delete_post_meta($object_id, '_featured_post');
}