How do you hook into WordPress save process for a post?

Using the save_post Action Hook

Definition:

• save_post fires after a post (any post type) is created or updated in the database.
• Lets you run custom code (e.g., saving metadata, triggering notifications) whenever a post is saved.

Basic Example

function my_save_post_callback( $post_id, $post, $update ) {
    // 1. Avoid running on autosave or revision
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;
    if ( wp_is_post_revision( $post_id ) ) return;

    // 2. Check user permissions
    if ( ! current_user_can( 'edit_post', $post_id ) ) return;

    // 3. Run your custom logic (e.g., save custom field)
    if ( isset( $_POST['my_custom_field'] ) ) {
        update_post_meta( $post_id, 'my_custom_field', sanitize_text_field( $_POST['my_custom_field'] ) );
    }
}
add_action( 'save_post', 'my_save_post_callback', 10, 3 );

Parameters

save_post passes 3 arguments:

1. $post_id → The ID of the post being saved.
2. $post → The post object.
3. $update → true if updating an existing post, false if creating a new one.

Best Practices

Always check for DOING_AUTOSAVE to avoid duplicate triggers.

Skip wp_is_post_revision() to avoid affecting post revisions.

Verify nonces for security if saving form data.

Use save_post_{post_type} for targeting specific post types.
Example:

add_action( 'save_post_product', 'my_product_save_callback', 10, 3 );

💡 Analogy:
Hooking into save_post is like installing a camera in the kitchen — you get notified every time a new dish is made or updated, so you can take action right away.