php学习笔记之面向对象编程

<?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();