gf-spam-check-with-entry-note.php

/**
 * Performs spam check and returns result to Gravity Forms.
 *
 * @param bool  $is_spam Indicates if the entry is to be marked as spam.
 * @param array $form    The form currently being processed.
 * @param array $entry   The entry being evaluated.
 *
 * @return bool
 */
function your_gform_entry_is_spam_callback( $is_spam, $form, $entry ) {
	// Return early if the entry has already been marked as spam by another plugin.
	if ( $is_spam ) {
		return $is_spam;
	}

	// Perform your spam check here; populating $is_spam with the result.

	if ( $is_spam ) {
		add_action( 'gform_entry_created', 'your_gform_entry_created_callback' );
	}

	return $is_spam;
}
add_filter( 'gform_entry_is_spam', 'your_gform_entry_is_spam_callback', 11, 3 );

/**
 * Adds a note to the entry once the spam status is set (GF 2.4.18+).
 *
 * @param array $entry The entry that was created.
 */
function your_gform_entry_created_callback( $entry ) {
	if ( rgar( $entry, 'status' ) !== 'spam' || ! method_exists( 'GFAPI', 'add_note' ) ) {
		return;
	}

	GFAPI::add_note( $entry['id'], 0, 'Your plugin short name', __( 'This entry has been marked as spam.', 'your-plugin-domain' ), 'your-plugin-slug', 'success' );
}