onsubmit javascript重新加载页面，但不会在Php中消除成功消息

I try to reload the page on the current page when submit the form to prevent from multiple data insert in each refresh the page. But the below code just reload the current page but does not display the successful message after the form submit successful. So pleas help me anyone to solve this problem. My html code for form is as below:-I try to reload the page on the current page wh