php学习笔记之面向对象编程

一个php初学者的一个学习笔记的面向对象编程实例，有需要学习的朋友可参考参考。

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代码如下

复制代码

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 " "; <br> print_r ( $chanelInfo ); <p>class a { <br>     protected  function aa(){ <br>         echo 222; <br>     } <br> } <br> class b extends a{ <br>     function bb(){ <br>         $this->aa(); <br>     } <br> } <br> $c = new b(); <br> $c->bb();</p>

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