php - PDO 查询不起作用

Question

我无法查询。

这是我的代码，我连接到数据库并尝试查询。

编辑 ：

class DatabaseConnection {
    private $host;
    private $port;
    private $dbname;
    private $username;
    private $password;
    private $query;


    function __construct($host, $port, $dbname, $username, $password) {
        $this->host = $host;
        $this->port = $port;
        $this->dbname = $dbname;
        $this->username = $username;
        $this->password = $password;

        try {
            $conn = new PDO("pgsql:host=$this->host port=$this->port dbname=$this->dbname", "$this->username", "$this->password");
            echo "PDO connection object created";
        }
        catch(PDOException $e) {
            echo $e->getMessage();
        }
    }


    function setQuery($query) {
        $this->query = $query;
        $sth = $db->prepare($this->query);
        $sth->execute();
        $result = $sth->fetchAll();
        var_dump($result);
    }

}

$db = new DatabaseConnection('144.76.6.45','5432','eu','eu','eu123');
$db->setQuery('SELECT * FROM user');

这是我的代码，我没有任何错误，但仍然无法正常工作.....

Answer 1

根据查询的类型，您将希望在执行后获取数据。看看fetch()和fetchAll()方法。

$sth = $db->prepare($this->query);
$sth->execute();
$result = $sth->fetchAll();
var_dump($result);

或使用循环并逐行获取

while ($row = $sth->fetch(PDO::FETCH_ASSOC)) {
    var_dump($row);
}

编辑后：

尝试替换：

$conn = new PDO("pgsql:host=$this->host port=$this->port dbname=$this->dbname", "$this->username", "$this->password");

和

$this->db = new PDO("pgsql:host=$this->host port=$this->port dbname=$this->dbname", "$this->username", "$this->password");

然后prepare在其上调用方法：$sth = $this->db->prepare($this->query);而不是$sth = $db->prepare($this->query);