pb fix option 1

[chc421]

Description

Re-order server parambuilder library load order

Type of change

Please delete options that are not relevant

• Fix (non-breaking change which fixes an issue)

Checklist

• I have commented my code, particularly in hard-to-understand areas, if any.
• I have confirmed that my changes do not introduce any new PHPCS warnings or errors.
• I have checked plugin debug logs that my changes do not introduce any new PHP warnings or FATAL errors.
• I followed general Pull Request best practices. Meta employees to follow this wiki.
• I have added tests (if necessary) and all the new and existing unit tests pass locally with my changes.
• I have completed dogfooding and QA testing, or I have conducted thorough due diligence to ensure that it does not break existing functionality.
• I have updated or requested update to plugin documentations (if necessary). Meta employees to follow this wiki.

Changelog entry

One liner entry to be surfaced in changelog.txt

Test Plan

Manual test
Test case 1 (New visitor):

• clear all browser cookie in incognito mode
• visit website
• verify fb cookies
• verify debug.log
  Test case 2 (Existing user):
• visit website
• verify fb cookies
• verify debu.log

Screenshots

Before

[17-Sep-2025 15:15:12 UTC] PHP Warning: Cannot modify header information - headers already sent in /Users/chenghaochen/Local Sites/local-color-crush/app/public/wp-content/plugins/facebook-for-woocommerce/facebook-commerce-events-tracker.php on line 203

After

[github-actions]

📦 Latest Plugin Build

Built at: 2025-09-26T02:19:22.793Z
Commit: 5fe84f5
Size: 1.4M

Download: Click here to download the plugin

To download: Click the link above → Scroll to bottom → Download "facebook-for-woocommerce" artifact

[ukilla]

After reviewing the param_builder_set_cookies and init_param_builder functions, I noticed that param_builder_set_cookies depends on the param_builder being initialized. Currently, with this fix, param_builder_set_cookies runs on the init hook at priority 1, while init_param_builder runs at priority 5. Since the cookie function relies on the param_builder, we need to run init_param_builder first, so increasing its priority to at least 6 ensures proper initialization before setting cookies. This priority should also prevent the “headers already sent” warning.

[chc421]

After reviewing the param_builder_set_cookies and init_param_builder functions, I noticed that param_builder_set_cookies depends on the param_builder being initialized. Currently, with this fix, param_builder_set_cookies runs on the init hook at priority 1, while init_param_builder runs at priority 5. Since the cookie function relies on the param_builder, we need to run init_param_builder first, so increasing its priority to at least 6 ensures proper initialization before setting cookies. This priority should also prevent the “headers already sent” warning.

Yes, you are right. I think I might found the issue. get_integration did not have a priority with it and it runs other add actions that triggers interaction with browser. The previous version eliminate many cases because we try to force param_builder_set_cookies run early but there's no guarantee. Lmk if there's other concerns.

[ukilla]

Right now we have the order:

1. init_param_builder
2. param_builder_set_cookies
3. get_integration

Given that the integration class mainly handles feed-related actions (syncing, updating, etc.), this order looks fine, and after testing I don't see any warnings that were reported previously.

One possible improvement: we could add lazy initialization inside get_param_builder(), similar to how get_integration() works. That way, we ensure the param builder is always available when requested, without relying strictly on hook priority.

public function get_param_builder() {
    if ( null === $this->param_builder ) {
        $this->init_param_builder();
    }

    return $this->param_builder;
}

[chc421]

iven that the integration class mainly handles feed-related actions (syncing, updating, etc.), this order looks fine, an

That's a good idea, now I can get rid of this https://github.com/facebook/facebook-for-woocommerce/blob/main/facebook-commerce-events-tracker.php#L194-L196.

[ukilla]

Hi @chc421,
I tested the flow again and can confirm both _fbp (always set) and _fbc (when fbclid is present) cookies are working correctly, and no warnings are triggered.

[chc421]

Hi @chc421, I tested the flow again and can confirm both _fbp (always set) and _fbc (when fbclid is present) cookies are working correctly, and no warnings are triggered.

Thank you for testing. Could you help me to stamp?