how to call another file in php code example

Example: php import function from another file

File1.php :
<?php
  function first($int, $string){ //function parameters, two variables.
    return $string;  //returns the second argument passed into the function
  }
?>
  
File2.php :
<?php
  include 'File1.php';
  echo first(1,"omg lol"); //returns omg lol;
?>