simple database class fit for simple CRUD application

database.php

<?php 

/*******
database class personalize 
author : besingamk
description: simple database class for simple CRUD application
driver : PDO
*/

class Database {
	protected $host = "localhost";
	protected $user = "root";
	protected $pass = "";
	protected $dbname = "login_db";
	protected $conn;

	private $sql_query;
	private $where = array();


	public function __construct() {
		$this->conn = new PDO("mysql:host=" . $this->host .";dbname=" . $this->dbname, $this->user, $this->pass);
		$this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
	}

	public function query($query = null) {
		$q = ($query == null) ? $query : $this->sql_query;
		$this->sql_query = $query;
	}

	public function show_query() {
		return $this->sql_query;
	}

	public function select($sql) {
		$this->sql_query .= "SELECT $sql";
		return $this;
	}

	public function from($table) {
		$this->sql_query .= " FROM $table";
		return $this;
	}

	public function where($field, $value, $cond = '=') {
		$dilimeter = ( @$this->where['is_set'] != true) ? 'WHERE' : 'AND';
		$this->where['is_set'] = true;
		//echo $dilimeter;
		$this->sql_query .= " " . $dilimeter . " $field $cond $value";
		return $this;
	}

	public function order_by($field, $asc = 'ASC') {
		$asc = (strtoupper($asc) != 'ASC') ? 'DESC' : 'ASC';
		$this->sql_query .= " ORDER BY $field $asc";
		return $this;
	}

	public function get() {
		try {
			$q = $this->conn->prepare($this->sql_query);
			$q->execute();
			$q->setFetchMode(PDO::FETCH_OBJ);
			return $q->fetchAll();
		} catch(PDOException $e) {
			die("ERROR: ".$e->getMessage());
		}
	}

	/*
	below is the code for insert function
	date 10-12-2014
	*/

	public function insert($table, $data) {
		$new_data = array();
		$fields = "";
		$values = "";
		foreach($data as $field_name => $value) {
			$new_data[":" . $field_name] = $value;
			$fields .= $field_name . ", ";
			$values .= ":".$field_name . ", ";
		}	
		$fields = substr($fields, 0, -2);
		$values = substr($values, 0, -2);

		try {
			$sql = "INSERT INTO $table ($fields) VALUES ($values)";
			$q = $this->conn->prepare($sql);
			$q->execute($new_data);
		} catch(PDOException $e) {
			die('ERROR: ' . $e->getMessage());
		}		
	}

	/*
	below is the code fo update function
	date 10-12-2014
	*/
	public function update($data) {
		// code goes here
	}
}

$a = new Database();
//$a->query("SELECT * FROM users");
$a->select("id")->from("users")->where('ulevel', '1')->order_by('id');
echo $a->show_query();
echo "<pre>";
print_r($a->get());

// $data = array(
// 	'username' => 'usersss',
// 	'password' => md5('password')
// );
// //$a->insert('users', $data);

// $a->where("yow", "waysup");

?>