Slava Rozhnev

<?php
class A
{
	protected $sql = null;
	
	public function setSQL()
    {
        $this->sql = "SELECT * FROM users WHERE id = 123";
        return $this;
    }
	
	public function getSQL()
    {
        return $this->sql;
    }
}

class B extends A
{
    public function addSQL()
    {
        $this->sql .= " AND name = 'Alex'";
		
		return $this;
    }
}
$a = new A();
$b = new B();

echo $b->setSQL()->addSQL()->getSQL();

$prod = [
 	'x' => new Phone('Iphone X ', '$1500 ', 'Phone ', 'Apple ', 'A9 ', '1024 ', '1 ', '128gb ', 'Ios '),
 	'mon' => new Monitor('Abracadabra ', '$1500 ', 'Monitor ', 'DELL ', '24 ', '144ghz ', 'HDMI '),
  	'mon1' => new Monitor('ROG ', '$1500 ', 'Monitor ', 'ASUS ', '24 ', '144ghz ', 'HDMI ')
];

foreach($prod as $p) $p->show();