Gravity forms before submission review page for all forms

review-page-for-all-forms.php

add_filter( 'gform_review_page', 'wpmonks_add_review_page', 10, 3 );
function wpmonks_add_review_page( $review_page, $form, $entry ) {
 
    // Enable the review page
    $review_page['is_enabled'] = true;
 
    if ( $entry ) {
        // Populate the review page
        $review_page['content'] = GFCommon::replace_variables( '{all_fields}', $form, $entry );
    }
 
    return $review_page;
}