PHP - Xml Simplexmlelement::__construct() Problem

Hi! I'm new here 

I'm following an online course where we building CMS using OOP PHP and PDO. I read some articles and watched a few youtube tutorials and to be honest, I'm pretty confused. Some of the developers suggest using function __construct(PDO $connection) inside the class.

Their code looks something like that:

  private PDO $connection;
  function __construct(PDO $connection) {
    $this->connection = $connection;

connect.php

class dbh{
    
        private $host = "localhost";
        private $user = "root";
        private $pwd = "";
        private $dbname = "cms";

        protected function connect() {
            $dsn = 'mysql:host=' . $this->host . ';dbname=' . $this->dbname;
            $pdo = new PDO ($dsn, $this->user, $this->pwd);
            $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
            return $pdo;

    }
}

function.php // not a whole code
 

class CategoriesData extends dbh{

    public function getAllCategories() {

			$sql = "SELECT * FROM categories_tbl";
			$stmt = $this->connect()->query($sql);
				while ($row = $stmt->fetch()){
				
				echo $row['category_name'] . '<br>';

		}
    }

 	public function getCategoryName() {

			$sql = "SELECT category_name FROM categories_tbl";
			$stmt = $this->connect()->prepare($sql);
			$stmt->execute();
			$category = $stmt->fetch(PDO::FETCH_OBJ);
			
			if($category == null) {

				return null;
			}else {

				return $category->category_name;
			}
    } 

	public function getCategoryDetials() {

			$sql = "SELECT * FROM categories_tbl";
			$stmt = $this->connect()->prepare($sql);
			$stmt->execute();
			$result = $stmt->fetchAll((PDO::FETCH_OBJ));
			
			return $result;
    }   
		
    public function addCategory ($filter_name, $filter_title, $filter_description, $filter_slug) {

			$sql = "INSERT INTO categories_tbl (category_name, category_title, category_description, category_slug) VALUES (?, ?, ?, ?)";
			$stmt = $this->connect()->prepare($sql);
			$stmt->execute([$filter_name, $filter_title, $filter_description, $filter_slug]);
 
		}

	public function deleteCategory($delete_category_id) {
			$sql =  "DELETE FROM categories_tbl WHERE category_id = ?";
			$stmt = $this->connect()->prepare($sql);
			$stmt->execute([$delete_category_id]);
    }
    }
       }
   

Guys thanks for helping me solve the problem i had but now i have another problem and i am lost. i have included the code below for you to have overview.

On the home page the url shows how it should be: http://localhost/board/italian.php?country=Italian
BUT 
When you mouse over the NEXT link to go to next page you get this : http://localhost/board/?page=1&country=Italian  and then an error 404 when you click on the link
page = 1  no matter if you are mousing over link for page 5 or 2

This is the code:

<table style="width:100%; margin-left:auto; margin-right:auto">
        <?php    
            
            $items_per_page = 5;//how many records/rows to display per page
                        
            $page_url      = "http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
                                    
            $cleaned_current_page_country = htmlspecialchars($_GET["country"]);
                        
            $page_number = (isset($_GET['page']))? filter_var($_GET['page']) : 1;
            //$page_number = filter_var($_GET['page']);
            //$page_number = $_GET['page'];
                
            $selected_restaurant_type = $_GET['country'];
                                                            
            // find number of rows in the db
                $query = "SELECT * FROM menu_update WHERE special_of_theday = 1 AND restaurant_type = '".$selected_restaurant_type."' ";
                $query_result = mysqli_query($connection, $query); 
                $row_count = mysqli_fetch_array($query_result);
                $total_rows = mysqli_num_rows($query_result);
                                                
            $expected_number_of_pages = ceil($total_rows/$items_per_page); //expected number of pages 
                                                
            $page_position = (($page_number - 1) * $items_per_page); //get starting position to fetch record
                        
            //fetch a group of records using sql LIMIT clause
                $query = "SELECT * FROM menu_update WHERE special_of_theDay = 1 AND restaurant_type = '".$selected_restaurant_type."' LIMIT " .$page_position. ',' .$items_per_page;
                $query_result = mysqli_query($connection, $query);
        ?>
                        
            <table width="100%" border=0>
                <tr bgcolor = "#cccccc">
                    <td>Meal</td>
                    <td>Meal name</td>
                    <td>Meal Price</td>
                    <td>Order Now</td>
                    <td>Full Menu</td>
                    <td>Our Gallery</td>
                    <td>Find Us</td>
                    <td>Our Chef</td>
                    <td>Our Manager</td>
                </tr>
        <?php
                while($row_count = mysqli_fetch_array($query_result)){
                    echo "<tr>";
                        echo"
                            <td style ='width:200px; text-align:center; height:120px; background:#eaedf2'><a href='meal_fullPic.php'><img src= ".$row_count['img']." /></a></td>
                            <td style ='width:119px; text-align:center; height:120px; background:#eaedf2'> ".$row_count['meal_name']."</td>
                            <td style ='width:100px; text-align:center; height:120px; background:#eaedf2'>".$row_count['price']."</td>
                            <td style ='width:100px; text-align:center; height:120px; background:#eaedf2'><a href='order_processor.php'><img src= ".$row_count['order_now']." /></a></td>
                            <td style ='width:100px; text-align:center; height:120px; background:#eaedf2'><a href='full_menu.php'><img src= ".$row_count['full_menu_img']." /></a></td>
                                    
                            <td style ='width:170px; text-align:center; height:120px; background:#eaedf2'><a href='restaurant_gallery.php'><img src= ".$row_count['restaurant_pic']." /></a></td>
                            <td style ='width:100px; text-align:center; height:120px; background:#eaedf2'><a href='restaurant_location.php'><img src= ".$row_count['location_pic']." /></a></td>
                            <td style ='width:119px; height:120px; background:#eaedf2'> ".$row_count['chef_name']."</td>
                            <td style ='width:119px; height:120px; background:#eaedf2'> ".$row_count['admin']."</td>
                        "; 
                    echo "</tr>";
                }
                mysqli_close($connection);
        ?>    
            </table>
        <div class="board_pagination">
        <?php
            //display the links to the pages
            for($current_page = 1; $current_page <= $expected_number_of_pages; $current_page++){
                 if ($page_number != $expected_number_of_pages){
                    $data = array(
                        'page' => $page_number,
                        'country' => $cleaned_current_page_country,
                    );
                    $the_query = http_build_query($data);
                    $page_url .= '?' . $the_query;
                    echo '<li><a href=" '.$the_query.' ">'.$current_page.'</a></li> ';
                }
            }
        ?>
        </div>
    </table>