我正在用PHP 5.6.6设计一个网页，试图使用一些OOP思想。当我在文件index.php中包含文件classnews.php时，我会得到错误
Undefined variable: connect in classtin.php
classdb.php：
<?php
class db
{
public $hostname = "localhost";
public $user= "root";
public $pass = "";
public $db = "test";
/* public $connect = NULL;
public $result = NULL;*/
function __construct()
{
$connect = mysqli_connect($this->hostname, $this->user, $this->pass,$this->db);
mysqli_set_charset($connect,'utf8');
}
}
?>
classnews.php：
<?php
include_once('classdb.php');
class tin extends db
{
public function tinmoi()
{
$sql= "select * from emp ";
$result= mysqli_query($connect,$sql);
return $result;
}
}
?>
您需要通过$this引用类成员。例如，与$this->hostname相同。
修改您的代码部分：
class db
{
public $hostname = "localhost";
public $user= "root";
public $pass = "";
public $db = "test";
public $connection;
public function __construct()
{
$this->connection = mysqli_connect($this->hostname, $this->user, $this->pass,$this->db);
mysqli_set_charset($this->connection,'utf8');
}
}
class tin extends db
{
public function tinmoi()
{
$sql = "select * from emp ";
return mysqli_query($this->connection, $sql);
}
}
再次，我强烈建议您学习PHP中OOP的基础知识：http://php.net/manual/en/language.oop5.basic.php