PHP Notice: Unidentified index

Question

When I create a new post of a Custom Post Type, my debug.log gets filled with PHP Notice: Unidentified index: warnings for each of the meta fields.

This question has been asked and answered before here and I implemented the solution there but each time I create a new post of this type, I am still seeing the errors in debug.log.

The code for the save method is as follows:

/** Listener for saving post */
public function save() {
    $post_type_name = $this->post_type_name;

    add_action( 'save_post',
       function () use ( $post_type_name ) {

            // Do not autosave meta box data
            if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
                return;
            }

            // Abort if the nonce field is not set
            if ( ! isset( $_POST['my-nonce'] ) ||
                 ! wp_verify_nonce( $_POST['my-nonce'], MY__PLUGIN_FILE ) ) {
                return;
            }

            global $post;

            if ( isset( $_POST ) && isset( $post->ID ) && get_post_type( $post->ID ) == $post_type_name ) {
                global $custom_fields;

                // Loop through all meta boxes
                foreach ( $custom_fields as $title => $fields ) {

                    // Loop through all fields in meta box
                    foreach ( $fields as $label => $type ) {

                        $field_name = self::uglify( $title ) . '_' . self::uglify( $label );

                        // Prevent PHP Warnings for undefined index
                        if ( isset( $_POST['fitcase'][ $field_name ] ) ) {
                            $metadata = $_POST['fitcase'][ $field_name ];
                        } else {
                            $metadata = null;
                        }

                        update_post_meta( $post->ID, $field_name, $metadata );
                     }
                 }
            }
        }   
    );
}

Answer 1

I dug deeper into the warnings and found that it was actually a different method in my class that was causing the error. I have one that creates fields within meta boxes and sets the value attribute to the content of $meta[ $field_id_name ][0]. This is what was causing the notice message.

So ahead of construction of the form element, I added the following:

// Check for meta data for value attribute and set to null if not found
if ( ! isset( $meta[ $field_id_name ] ) ) {
    $meta[ $field_id_name ][0] = null;
}

I ran it through a test with several loads of a new post and with one with pre-existing metadata and it works.