Change description on specific WooCommerce product status change

Question

In WooCommerce, when I add couple of code lines to change the product description, on product status change, the website throw an error when submitting (saving).

My code:

add_action('transition_post_status', 'new_product_add', 10, 3);
function new_product_add($new_status, $old_status, $post) {
    if( 
        $old_status != 'publish' 
        && $new_status == 'pending' 
        && !empty($post->ID) 
        && in_array( $post->post_type, 
            array( 'product') 
        )
    ) {
        $term = get_term_by('name', 'فروش پیج اینستاگرام', 'product_cat');
        wp_set_object_terms($post->ID, $term->term_id, 'product_cat', true);

        /******************************/
        $product = wc_get_product($post->ID);
        $product->set_description("something");
        $product->save();
        /******************************/
    }
}

as you see, these last 3 lines lead to the problem the page refreshes and also update the product description but give me and error

“THE SITE IS EXPERIENCING TECHNICAL DIFFICULTIES”

and when I remove them it works okay and show me the successful message

UPDATE

I changed these 3 line with Wordpress way

wp_update_post( array('ID' => $post->ID, 'post_content' => "something"));

still do the job but instead of successful message gives me this technical error

UPDATE II

When I open Chrome console I see this error also

Failed to load resource: the server responded with a status of 500 () (index):1

Answer 1

To avoid an infinite loop on transition_post_status hook when using wp_update_post(), try:

add_action('transition_post_status', 'new_product_add', 10, 3);
function new_product_add($new_status, $old_status, $post) {
    if( 
        $old_status != 'publish' 
        && $new_status == 'pending' 
        && !empty($post->ID) 
        && $post->post_type === 'product'
    ) {
        $term = get_term_by('name', 'فروش پیج اینستاگرام', 'product_cat');
        wp_set_object_terms($post->ID, $term->term_id, 'product_cat', true);

        // unhook this function so it doesn't loop infinitely
        remove_action( 'transition_post_status', 'new_product_add', 10 );

        wp_update_post( array('ID' => $post->ID, 'post_content' => "something"));

        // re-hook this function
        add_action( 'transition_post_status', 'new_product_add', 10, 3 );
    }
}

Or:

add_action('transition_post_status', 'new_product_add', 10, 3);
function new_product_add($new_status, $old_status, $post) {
    if( 
        $old_status != 'publish' 
        && $new_status == 'pending' 
        && !empty($post->ID) 
        && $post->post_type === 'product'
    ) {
        $term = get_term_by('name', 'فروش پیج اینستاگرام', 'product_cat');
        wp_set_object_terms($post->ID, $term->term_id, 'product_cat', true);

        $product = wc_get_product($post->ID);

        // unhook this function so it doesn't loop infinitely
        remove_action( 'transition_post_status', 'new_product_add', 10 );

        $product->set_description("something");
        $product->save();

        // re-hook this function
        add_action( 'transition_post_status', 'new_product_add', 10, 3 );
    }
}

It may solve your issue.

This is documented here on wp_update_post() for save_post hook.