How To Make A PHP Include Function Within A Post

Thanks in advance for any guidance.

Goal:
Add a simple php include in a post and have it actually work.

Issue:
I used to use simple php includes in custom websites, but when I put php include code in a post, it nullifies the php code.

Is there a proper way to add php include code in a WP post or should one use a PHP include plugin to get the job done? ( I know there’s a few out there, but wanted to make sure that was the route to go before implementing a plugin)

Thanks for your guidance!