การเขียนโค้ดไปไม่เป็นแล้วคับ Register&Login ช่วยหน่อยคับ ยิ่งเขียนยิ่งมึน

<?php
class Member {
	private $DB;
	function __construct($db) {
		$this->DB = $db;
	}
	
	public function signupMember($param){
		$ret = $this->_signupMember($param);
		return $ret;
	}
	public function C_Pass($param){
		$ret = $this->PC_Pass($param);
		return $ret;
	}
	public function checkParam($param){
		$ret = $this->_checkParam($param);
		return $ret;
	}
	public function check_Username($param){
		$ret = $this->_check_Username($param);
		return $ret;
	}
	private function _signupMember($param){
		
	}
	private function PC_Pass($param){
		$password = $param['password'];
		$re_password = $param['re-password']; 
		if($password==$re_password){
			return true;
		}
		else{
			return false;
		}
	}
	private function _checkParam($param){
		$firstname = $param['firstname'];
		$lastname = $param['lastname'];
		$emailuse = $param['emailuse'];
		$username = $param['username'];
		$sex = $param['sex'];
		$accept = $param['accept'];
		$password = $param['password'];
		$re_password = $param['re-password'];
		if(empty($accept)){
			$rt = false;
			return $rt;exit();
		}
		else if($firstname==""){
			$rt = false;
			return $rt;exit();
		}
		else if(empty($lastname)){
			$rt = false;exit();
		}
		else if(empty($sex)){
			$rt = false;
			return $rt;exit();
		}
		else if(empty($password)){
			$rt = false;
			return $rt;exit();
		}
		else if(empty($emailuse)){
			$rt = false;
			return $rt;exit();
		}
		else if(empty($username)){
			$rt = false;
			return $rt;exit();
		}	
		else if(!$password==$re_password){
			$rt = false;exit();
		}else{
			
			
		}
		
		
	}
	private function _check_Username($param){
		$username = $param['username'];
		$SQL = "SELECT 	username FROM  user  WHERE username =".$username;
		$rs = $this->DB->Execute($SQL);
		if($rs){
			echo "";
		}else{
			echo "";
		}	
	}
}
?>