wp-includes/class-wp-hook.php:271Checks if any callbacks have been registered for this hook.
bool public function has_filters() { foreach ( $this->callbacks as $callbacks ) { if ( $callbacks ) { return true; } } return false; }Introduced in 4.7.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-hook.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.