DatabaseMapperWithAttributes.php

<?php

class DatabaseMapper
{
    public function map(array $row, string $class)
    {
        // these lines until the foreach ($row) loop only need to be done once per class
        $reflection = new ReflectionClass($class);

        $properties = [];
        $columnPrefixes = [];
        $associationClasses = [];

        foreach ($reflection->getProperties() as $property) {
            $properties[strtolower($property->getName())] = $property;

            $association = $property->getAttributes(AssocationColumnPrefix::class);

            if (count($association) > 0) {
                $assocationAttribute = $association[0]->getAsObject();

                $columnPrefixes[$property->getName()] = $assocationAttribute->prefix;
                $associationClasses[$property->getName()] = $associationClasses->class;
            }
        }

        // this needs to be done per row
        $object = $reflection->newInstance();

        $associationColumns = [];

        foreach ($row as $column => $value) {
            $property = str_replace("_", "", $column);

            if (!isset($properties[$property])) {
                continue;
            }

            if (!isset($columnPrefixes[$property])) {
                // no column prefix? We assume its a regular field
                $reflection->getMethod("set" . $property)->invoke($object, $value);
            } else {
                // we check if it matches a column prefix and store it for each
                // assocation
                foreach ($columnPrefixes as $associationProperty => $columnPrefix) {
                    if (strpos($column, $columnPrefix) === 0) {
                        // column prefix matched, such as "category_"
                        $associationColumn = str_replace($columnPrefix, "", $column);
                        $associationColumns[$associationProperty][$associationColumn] = $value;

                        break 2;
                    }
                }
            }
        }

        // now iterate all the associations we found, map and assign them
        foreach ($associationColumns as $associationProperty => $row) {
            $relatedObject = $this->map($row, $associationClasses[$associationProperty]);
            $reflection->getMethod("set" . $associationProperty)->invoke($object, $relatedObject);
        }

        return $object;
    }
}

class AssocationColumnPrefix implements \Php\Attribute
{
    public $prefix;
    public $class;

    public function __construct(string $prefix, string $class) {
        $this->prefix = $prefix;
        $this->class = $class;
    }
}

class Post
{
    private $id;
    private $name;
    private $slug;
    private $content;

    <<AssocationColumnPrefix("category_", Category::class)>>
    private $category;
}

$sql = 'SELECT p.id, p.name, p.slug, p.content, p.category_id, p.cateogry_name FROM post p JOIN category c ON c.id = p.category_id WHERE p.id = ?';
$stmt = $pdo->prepare($sql);
$stmt->bindParam(1, $_GET['id']);
$stmt->execute();

$mapper = new DatabaseMapper();
$post = $mapper->map($stmt->fetch(), Post::class);