<?php
class DB {
    var $query;
    var $sql;
    public function __construct() {
        $this->sql = new mysqli("localhost", "root", "", "database");
    }
    public function update($tab) {
        $this->query .= "UPDATE " . $tab;
    }
    public function set($set) {
        $this->query .= " SET " . $set;
    }
    public function where($where) {
        $this->query .= " WHERE " . $where;
    }
    public function execute() {
        echo $this->query;
    }
}
$db = new DB();
$db->update("user");
$db->set("nome='arturo'");
$db->where("id=25");
$db->execute();
?>