如何将一些PHP行转换为函数和调用？

Question

I get this lines on web and just created a function name to that. The problem is: it is not working anymore and I dont know why, already tried things but nothing. Can someone help me please?

Code:

 <?php
    require 'PDOClasses/connection.php';
    error_reporting(E_ALL);
    ini_set('display_errors', 1);

    function ShowCategories() {
        $query = $db->query("SELECT id, name FROM categories ORDER BY name ASC");
        $option = '';
        while($row = $query->fetch(PDO::FETCH_ASSOC)) {
            $option .= '<option value = "'.$row['id'].'">'.$row['name'].'</option>';
        }
    }
?>

This is how I used to call:

<select id="category" name="category" tabindex="16" required>
   <?php echo $option; ?>
</select>

This is how I'm calling now:

<select id="category" name="category" tabindex="16" required>
   <?php ShowCategories(); ?>
</select>

Answer 1

You are neither returning the value inside the function or echoing it.Do it like this

function ShowCategories() {
        $query = $db->query("SELECT id, name FROM categories ORDER BY name ASC");
        $option = '';
        while($row = $query->fetch(PDO::FETCH_ASSOC)) {
            $option .= '<option value = "'.$row['id'].'">'.$row['name'].'</option>';
        }
        return $option;
    }

Then while calling

<select id="category" name="category" tabindex="16" required>
   <?php echo ShowCategories(); ?>
</select>

or you can directly echo the $option inside the function itself.Like

echo $options;

instead of returning it.