wordpress_save_posts.php

/**
* Saves the meta box field data
*
* @param int $post_id Post ID
*/
function save_meta_boxes( $post_id ) {
 
    // Check if our nonce is set.
    if ( ! isset( $_POST['{name}_nonce'] ) ) {
        return $post_id;    
    }
 
    // Verify that the nonce is valid.
    if ( ! wp_verify_nonce( $_POST['{name}_nonce'], '{save_post}' ) ) {
        return $post_id;
    }
 
    // Check this is the Contact Custom Post Type
    if ( '{post_type_name}' != $_POST['post_type'] ) {
        return $post_id;
    }
 
    // Check the logged in user has permission to edit this post
    if ( ! current_user_can( 'edit_post', $post_id ) ) {
        return $post_id;
    }
 
    // OK to save meta data
    $email = sanitize_text_field( $_POST['contact_email'] );
    update_post_meta( $post_id, '_contact_email', $email );
     
}