Method chaining PDO abstract DB layer

dbLayer.class.php

<?php
class dbLayer {
	
	private $hostname;
	private $username;
	private $password;
	private $dbname;
	
	private $current_query;
	private $validQuery; // while not perfect should be good enough to say if we have chosen a starter and finisher atleast.
	private $param;
	
	private $link; // DB link
	
	/*
	 * @param string $hostname -- server db resides on
	 * @param string $username -- username to for server & database
	 * @param string $password -- password for the user
	 * @param string $dbname -- database to connect to.
	 * 
	 * @return null -- returns nothing.
	 */  
	function __construct ($hostname,$username,$password,$dbname) {
		//Connection details	
		$this->hostname = $hostname;
		$this->username = $username;
		$this->password = $password;
		$this->dbname = $dbname;
		//Default members
		$this->_initQuery();
	}
	function _initQuery() {
		$this->current_query = "";
		$this->params = NULL;
		$this->validQuery = false;
		$this->param = NULL;
	}
	function _printQuery() {
		echo "{$this->current_query} <br />Params: ";print_r($this->param);	
	}
	function connect() {
		$this->link = new PDO("mysql:host={$this->hostname};dbname={$this->dbname}", $this->username, $this->password);
		return $this;
	}
	#Query Starters
	function select() {
		$this->_initQuery();
		$tblColumns = func_get_args();
		if (is_array($tblColumns))
			$args = implode("`, `", $tblColumns);
		else
				$args = $tblColumns;
		$this->current_query = "SELECT `{$args}` ";
		return $this;
	}
	#Query Finishers
	function from($dbTable) {
		if (empty($this->current_query)) {
			$this->last_error = "Error with ".__FUNCTION__." : Check your starters before using finishers.<br />Current Query: {$this->current_query}";
			return false;
		}
		$this->current_query .= "FROM `{$dbTable}` ";
		return $this;
	}
	function where ($data) {
		if (empty($this->current_query)) {
			$this->last_error = "Error with ".__FUNCTION__." : Check your starters and finishers.<br />Current Query: {$this->current_query}";
			return false;
		}
		//$params = array(':username' => 'test', ':email' => $mail, ':last_login' => time() - 3600);
		
		$this->current_query .= "WHERE ";
		
		foreach ($data as $k=>$v) {
			$firstchar = substr($v, 0, 1);
			if (in_array($firstchar, array("=","<",">","<>","=>","=<"))) {
				$this->current_query .= "`{$k}` {$firstchar} :{$k}"; 
				$this->param[":{$k}"] = $v;
			} else{ // default to equal to
				$this->current_query .= "`{$k}` = :{$k}"; 
				$this->param[":{$k}"] = $v;
			} 
				
		}
		return $this;
	}
	function results ( $type='array' ) {
		if (!$this->validQuery || empty($this->current_query)) {
			$this->last_error = "Error with ".__FUNCTION__." : Check your starters and finishers.<br />Current Query: {$this->current_query}";
			return false;
		} 
		$this->link->prepare($this->current_query);
		$this->link->execute($this->params);
		switch ($type) {
			case "array":
				break;
			default: 
				break;
		}
	}
}
?>