A few other tasks, such as Zephir, give the ability for PHP expansions to be created in a top-level language as well as compiled into native PHP expansions. Such a method, as opposed to writing PHP extensions directly in C, streamlines the development of extensions and reduces the time needed for programs and testing. PHP's single-request-per-script-execution model, and also the fact the Zend Engine is an interpreter, results in ineffectiveness; because of this, different products have actually been developed to assist improve PHP efficiency.