you can use $stmt = $mysqli->prepare(); directly without stmt-init() . i think there is no need for stmt-init .
mysqli::stmt_init -- mysqli_stmt_init — Initializes a statement and returns an object for use with mysqli_stmt_prepare
Allocates and initializes a statement object suitable for mysqli_stmt_prepare().
Any subsequent calls to any mysqli_stmt function will fail until mysqli_stmt_prepare() was called.
Returns an object.