PHP notices header already sent

I have now narrowed down the issue and after deactivating ALL plugins and tested 3 different theme versions (woodmart) i still get the notices but now they look like this:

[01-Oct-2019 16:51:55 UTC] PHP Notice: wp_woocommerce_session_59f9adf68b3deeb3d144141c2fae7308 cookie cannot be set – headers already sent by /wp-includes/class.wp-scripts.php on line 209 in /wp-content/plugins/woocommerce/includes/wc-core-functions.php on line 887

The above notice appear in v4.0.4 and 4.1.0 but not in v3.8.2 or any standard themes.

Brgds
Rune

Oki, its just annoying when using debug-log actively as it fills up with thousands of lines in a few days.

I have found that they appear only in archive pages and they appear even if i have deactivated wishlist, compare, header banner and promo popup.

Yes i have it enabled because i am using it actively when building websites. If i turn it of i will not be able to follow up on any issues during my development.

Rune

Development and testing is always done in my staging sites but sometimes, like yesterday, i had to debug a payment gateway issue which only appeared for some users on specific browsers then i had to enable it in my live site a few hours. But log was difficult to read as the record i was looking for was in between 2-3000 lines of this cookie notices. It adds up extremely fast in my live site because it has high traffic.

It is just annoying nothing else 😉

Rune

I just did a test in /wp-content/themes/woodmart/inc/integrations/woocommerce/functions.php

I commented out the add_action as below and issue dissapeared. isn it a little late to set session cookie “woodmart_before_shop_page” as other html has already been output?

if( ! function_exists( 'woodmart_set_customer_session' ) ) {

	//add_action( 'woodmart_before_shop_page', 'woodmart_set_customer_session', 10 );

	function woodmart_set_customer_session() {
		if( ! function_exists( 'WC' ) ) return;
		if ( WC()->version > '2.1' && ( ! is_admin() || defined( 'DOING_AJAX' ) ) && ! defined( 'DOING_CRON' ) ) :
			WC()->session->set_customer_session_cookie( true );
		endif;
	}

}

Sorry, forgot to mention that also this line:

if( ! function_exists( 'WC' ) ) return;

Needs to be changed to this:

if( ! is_shop() || ! function_exists( 'WC' ) ) return;

To avoid possible unconditional fatal errors.

Brgds
Rune