php PDO prepare()处理非对象错误

Question

我一直收到“致命错误:对/var/www/html/portal_core/build_portal.php中非对象上的成员函数准备()的调用”。我是PDO的新手，我真的把它当做一个测试来理解它。你们能帮我弄清楚我做错了什么吗？

 <?php

class build_portal 
{
protected $dbh; 

function __construct($dbname,$theme)
{
    try
    {
    $dbh = new PDO('mysql:dbname='.$dbname.';host=localhost',"username","password");
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $this->log_error("Construct 1st Try statement 3rd Line");
    }
    catch (PDOException $e)
    {
        echo "Page Could Not Be Loaded";
        return -1;
    }



}

function log_error($cause)
{
    try
    {
    $sth = $this->dbh->prepare("SELECT * from portal_errors");
    $sth->setFetchMode(PDO::FETCH_ASSOC);
    $sth->execute();
    }
    catch (PDOException $e)
    {
        print_r($e->errorInfo);
    }
}

} ?>

Answer 1

这看起来是一个范围问题。你应该在构造函数中将dbh赋值给$this->dbh。稍后在log_error()中访问它时，您希望它是一个类属性，但它最初是在构造函数中定义为局部变量的。

$this->dbh = new PDO('mysql:dbname='.$dbname.';host=localhost',"username","password");
$this->dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);