wp-includes/class-wpdb.php:4049Closes the current database connection.
bool public function close() { if ( ! $this->dbh ) { return false; } $closed = mysqli_close( $this->dbh ); if ( $closed ) { $this->dbh = null; $this->ready = false; $this->has_connected = false; } return $closed; }Introduced in 4.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wpdb.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.