wp-includes/class-wp-hook.php:461Determines whether an offset value exists.
$offsetmixedbool #[ReturnTypeWillChange] public function offsetExists( $offset ) { return isset( $this->callbacks[ $offset ] ); }Introduced in 4.7.0. One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
$offset retyped from mixed to int.verified against sourcesrc/wp-includes/class-wp-hook.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.