Tips eerste OOP scriptje

<?php

class mysql
{	
	public function __construct($server = '', $username = '', $password = '')
	{
		mysql_connect($server, $username, $password);		
	}
	
	public function Select_Db($db = '')
	{
		if(!empty($db))
		{
			mysql_select_db($db);
		}
		else
		{
			echo 'Please specify a database.';
		}
	}
}

?>

<?php

class phonebook
{
	public $number;
	public $name;
	
	public function __construct()
	{		
		if($_SERVER['REQUEST_METHOD'] == "POST")
		{
			$this->ProcessForm();
		}
		
		if(isset($_GET['id']) && !empty($_GET['id']))
		{
			$this->ShowDetails();
		}
		else
		{
			$this->ShowList();
			
			if($_GET['action'] == "add")
			{
				$this->ShowForm();
			}
			else
			{
				echo '<a href="?action=add">Add person</a>';
			}
		}		
	}
	
	public function ProcessForm()
	{
		if(!empty($_POST['name']) && !empty($_POST['number']))
		{
			$query = "INSERT INTO persons (name, number) VALUES('".htmlspecialchars(mysql_real_escape_string($_POST['name']))."', '".htmlspecialchars(mysql_real_escape_string($_POST['number']))."')";
			$result = mysql_query($query) or die(mysql_error());
			
			if($result)
			{
				echo 'The person has been added to the phonebook.';
			}
			else
			{
				echo 'Something went wrong while trying to add the new person to the phonebook.';
			}
		}
		else
		{
			echo 'You have to fill in all the fields.';
		}
	} 
	
	public function ShowList()
	{
		$query = "SELECT id, name, number FROM persons";
		$result = mysql_query($query) or die(mysql_error());
		
		if(mysql_num_rows($result) > 0)
		{
			echo '
			<table border="1">
			<tr>
			<td width="60">Name</td><td width="110">Number</td><td width="30">Detail</td>
			</tr>';
			
			while($row = mysql_fetch_assoc($result))
			{			
				echo '
				<tr>
				<td>'.$row['name'].'</td><td>'.$row['number'].'</td><td align="center"><a href="?id='.$row['id'].'">X</a></td>
				</td>
				</tr>';
			}
			echo '</table><br />';
		}
		else
		{
			echo 'No records present.<br /><br />';
		}
	}
	
	public function ShowDetails()
	{
		$query = "SELECT name, number FROM persons WHERE id = '".$_GET['id']."'";
		$result = mysql_query($query) or die(mysql_error());
		
		if(mysql_num_rows($result) == 1)
		{
			$row = mysql_fetch_assoc($result);
			
			echo 'Name: '.$row['name'].'<br />';
			echo 'Number: '.$row['number'].'<br /><br />';
		}
		else
		{
			echo 'This record doesn\'t exist.';
		}
	}
	
	public function ShowForm()
	{
		echo '
		<form action="" method="post">
		Name: <input name="name" type="text" /><br />
		Number: <input name="number" type="text" /><br /><br />
		<input name="Submit" type="submit" value="Submit" id="Submit" />
		</form>';
	}
}

?>