Challenge 1 — Solution

Task: Describe (in comments, since this is a single-file exercise) a
two-file setup: greeting.php defines a function sayHello($name), and
main.php uses require_once to load it and calls sayHello() with your
own name. Write out both files' full code as comments to show the
structure.

<?php
    // ---- greeting.php ----
    // <?php
    //     function sayHello($name) {
    //         return "Hello, " . $name . "! Welcome to the site.";
    //     }
    // ?>

    // ---- main.php ----
    // <?php
    //     require_once 'greeting.php';
    //     echo sayHello('Philip');
    // ?>

    // Since this is a single-file exercise, the two files above are
    // shown as commented-out code to illustrate the structure. A real
    // working equivalent, combined into one file for testing:
    function sayHello($name) {
        return "Hello, " . $name . "! Welcome to the site.";
    }

    echo sayHello('Philip');
?>


Output:
Hello, Philip! Welcome to the site.

Notes:
- In the real two-file version, main.php never defines sayHello()
  itself - it only becomes available once require_once 'greeting.php'
  has run, pulling greeting.php's own code into main.php's scope.
- require_once is the right choice here rather than plain include,
  since main.php genuinely cannot call a function that was never
  defined - if greeting.php were missing, the whole script should stop
  with a clear fatal error rather than silently continuing.
- The combined single-file version at the bottom produces the identical
  output the real two-file setup would, since include/require simply
  paste the target file's code in at that exact point.