PHP 8.5: TypeError in CustomerDataTrait — strict_types return type mismatch

[theMosaad]

Bug Description

CustomerDataTrait::get_customer_key() and CustomerDataTrait::get_customer_email() in inc/Engine/License/API/CustomerDataTrait.php declare string return types. The file uses declare(strict_types=1).

However, both methods return values from Options_Data::get() and rocket_get_constant(), which return mixed. On PHP 8.5, when the stored value is not strictly a string (e.g., an integer from the database), this causes a fatal TypeError:

TypeError: CustomerDataTrait::get_customer_key(): Return value must be of type string, int returned

Steps to Reproduce

1. Install WP Rocket 3.20.5 on PHP 8.5
2. Activate WP Rocket with a valid license
3. Visit any page — the TypeError is triggered during license validation

Expected Behavior

Methods should return a string without throwing a TypeError.

Proposed Fix

Add explicit (string) casts to the return values in both methods. This is backwards-compatible — casting a string to string is a no-op on older PHP versions.

 protected function get_customer_key(): string {
     return ! empty( $this->options->get( 'consumer_key', '' ) )
-        ? $this->options->get( 'consumer_key', '' )
-        : rocket_get_constant( 'WP_ROCKET_KEY', '' );
+        ? (string) $this->options->get( 'consumer_key', '' )
+        : (string) rocket_get_constant( 'WP_ROCKET_KEY', '' );
 }

 protected function get_customer_email(): string {
     return ! empty( $this->options->get( 'consumer_email', '' ) )
-        ? $this->options->get( 'consumer_email', '' )
-        : rocket_get_constant( 'WP_ROCKET_EMAIL', '' );
+        ? (string) $this->options->get( 'consumer_email', '' )
+        : (string) rocket_get_constant( 'WP_ROCKET_EMAIL', '' );
 }

I'll submit a PR with this fix shortly.

Environment

• WP Rocket version: 3.20.5
• PHP version: 8.5
• WordPress version: 6.9.1