php学习笔记之面向对象编程

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 "

"; 
print_r ( $chanelInfo );

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

public   公有的：本类，子类，外部对象都可以调用 
protected 受保护的：本类 子类，可以执行，外部对象不可以调用 
private 私有的：只能本类执行，子类与外部对象都不可调用