First, understand that you have three languages working together.
(首先，要了解您有三种语言协同工作。)
PHP: Is only run by the server and responds to requests like clicking on a link (GET) or submitting a form (POST).
(PHP：仅由服务器运行并响应请求，例如单击链接（GET）或提交表单（POST）。)
HTML & JavaScript: Is only run in someone's browser (excluding NodeJS).
(HTML和JavaScript：仅在某人的浏览器中运行（不包括NodeJS）。)
I'm assuming your file looks something like:
(我假设你的文件看起来像：)
<html>
<?php
function runMyFunction() {
echo 'I just ran a php function';
}
if (isset($_GET['hello'])) {
runMyFunction();
}
?>
Hello there!
<a href='index.php?hello=true'>Run PHP Function</a>
</html>
Because PHP only responds to requests (GET, POST, PUT, PATCH, and DELETE via $_REQUEST), this is how you have to run a PHP function even though they're in the same file.
(因为PHP只响应请求（通过$ _REQUEST获取GET，POST，PUT，PATCH和DELETE），所以即使它们在同一个文件中，也必须运行PHP函数。)
This gives you a level of security, "Should I run this script for this user or not?".(这为您提供了一定程度的安全性，“我是否应该为此用户运行此脚本？”。)
If you don't want to refresh the page, you can make a request to PHP without refreshing via a method called Asynchronous JavaScript and XML (AJAX).
(如果您不想刷新页面，可以通过名为Asynchronous JavaScript and XML（AJAX）的方法向PHP发出请求，而无需刷新。)
That is something you can look up on YouTube though.
(这是你可以在YouTube上查找的内容。)
Just search "jquery ajax"(只需搜索“jquery ajax”)
I recommend Laravel to anyone new to start off right: http://laravel.com/
(我推荐Laravel给任何新人开始吧： http ：//laravel.com/)
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