将功能代码添加到特定的php页面中

Question

I'm trying to add this code into my theme's function.php

function custom_add_author() {
    $author = get_the_author();
    echo $author; 
}

add_action( '???', 'custom_add_author' );

I wanted to add this function code into the specific php named "author-listing.php"

How can I add this using the correct code? was it?

add_action( 'author-listing.php', 'custom_add_author' );

Answer 1

If i read your question right..you can just use include() function.

For example at the top of author-listing.php, you can add:

include("function.php");