Question: I want to write a PHP code snippet in the question or answer. I searched that but Stack Overflow can insert only HTML, CSS, JavaScript snippet code.

How can I insert a PHP code snippet like below?

JavaScript snippet example:

```js
console.log('hello world');
```

Answer: 
If you understand the difference between client- and server-side code and the security implications thereof, you will understand why this is not, and probably never will be, a feature on Stack Overflow.
There isn't any way to run PHP code. You have to insert an additional link in your question/answer to share your PHP code snippet with fellow members.

A PHP code snippet can be shared by using the following websites:

<http://www.writephponline.com/>

<http://phptester.net/> - [My choice]

<https://www.mycompiler.io/online-php-compiler>

<https://paiza.io/en/languages/online-php-editor>

And many more. You can also google for this using "PHP code snippets online" keywords ;)