php面向对象编程的学习笔记

<?php
class db {
??? private $mysqli; //数据库连接
??? private $options; //SQL选项
??? private $tableName; //表名
??? public function __construct($tabName) {
??????? $this->tableName = $tabName;
??????? $this->db ();
??? }
??? private function db() {
??????? $this->mysqli = new mysqli ( 'localhost', 'root', '', 'hdcms' );
??????? $this->mysqli->query("SET NAMES GBK");
??? }
??? public function fields($fildsArr) {
??????? if (empty ( $fildsArr )) {
??????????? $this->options ['fields'] = '';
??????? }
??????? if (is_array ( $fildsArr )) {
??????????? $this->options ['fields'] = implode ( ',', $fildsArr );
??????? } else {
??????????? $this->options ['fields'] = $fildsArr;
??????? }
??????? return $this;
??? }
??? public function order($str) {
??????? $this->options ['order'] = "ORDER BY " . $str;
??????? return $this;
??? }
??? public function select() {
??????? $sql = "SELECT {$this->options['fields']} FROM {$this->tableName}? {$this->options['order']}";
??????? return $this->query ( $sql );
??? }
??? private function query($sql) {
??????? $result = $this->mysqli
??????????? ->query ( $sql );
??????? $rows = array ();
??????? while ( $row = $result->fetch_assoc () ) {
??????????? $rows [] = $row;
??????? }
??????? return $rows;
??? }
??? private function close() {
??????? $this->mysqli
??????????? ->close ();
??? }
??? function __destruct() {
??????? $this->close ();
??? }
}
$chanel = new db ( "hdw_channel" );
$chanelInfo = $chanel->fields ( 'id,cname,cpath' )
??? ->select ();
echo "<pre>";
print_r ( $chanelInfo );

?

class a {
??? protected? function aa(){
??????? echo 222;
??? }
}
class b extends a{
??? function bb(){
??????? $this->aa();
??? }
}
$c = new b();
$c->bb();