I make a login and registration function. (Registration function) I use

<script type="text/javascript" src="reg.php?id" in the HTML file (reg.html) =reg"></script>

<script type="text/javascript" src="reg.php"></script> (tried both)

Connect to the PHP file (reg.php), and then there is no interaction between the front and back ends during the test. When there are no code errors in the HTML file and PHP file, what is the problem? According to my own ideas, is it right? There is no trigger button written in the HTML file to trigger the code in the PHP file (meaning to get a button, click it and trigger the PHP file code effect), and is it possible that the above connection is wrong