PDO查询不起作用

Question

I can't do a query.

This is my code, where I connect to database and try to query.

EDIT :

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');

This is my code, I don't have any errors, but still it doesn't work.....

Answer 1

Depending on the type of query you will want to fetch data after executing it. Take a look at fetch() and fetchAll() methods.

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

or use a loop and fetch row by row

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

after your edit :

Try to replace:

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

with

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

and then call prepare method on it: $sth = $this->db->prepare($this->query); instead of $sth = $db->prepare($this->query);