php - PDO 查询返回空

Question

我有一个连接类文件，它允许我的其他类“函数”连接到我的 MySQL 数据库。但是，当我执行 MySQL 查询时，它仅返回 Array () 。事实上，我选择的数据就在那里(我检查过)。可能是什么问题？

连接.php

 <?php

 class Connection extends PDO {

 private $username;
 private $password;
 private $database;
 private $hostname;

 public function __construct($hostname, $username, $password, $database) {

    $this->hostname = $hostname;
    $this->username = $username;
    $this->password = $password;
    $this->hostname = $hostname;

    try {
        parent::__construct("mysql:host=" . $this->hostname . ";dbname=" . $this->database, $this->username, $this->password);
    }

    catch (PDOException $e) {
        echo $e->getMessage();
    }
  }
}

?>

函数.php

<?php

require_once "Connection.php";

class Functions {

private $connection;

public function __construct() {
    $this->connection = new Connection("127.0.0.1", "xxx", "xxx", "xxx");
}

public function sqlFetchAssoc($query) {

    $sth = $this->connection->prepare($query);
    $sth->execute();
    $result = $sth->fetchAll(PDO::FETCH_ASSOC);

    return $result;
    }
}

$functions = new Functions();
$row = $functions->sqlFetchAssoc("SELECT * FROM chatlogs WHERE id = 70");

print_r($row);

?>

Answer 1

我刚刚在 Connection.php 中发现了您的错误:

$this->hostname = $hostname;
$this->username = $username;
$this->password = $password;
$this->hostname = $hostname;

$this->hostname 重复，而 $this->database 未设置。但是，您可以完全删除 $this->something 的设置，因为您在同一函数中使用这些值。这将使事情变得更简单:

try {
    parent::__construct("mysql:host=" . $hostname . ";dbname=" . $database, $username, $password);
}

我建议更进一步。您应该分别测试每个类。您可以编写此脚本并在 testfunction.php 中对其进行调试(如果需要):

<?php
class Functions {
private $connection;

public function __construct() {
    $this->connection = new PDO("mysql:host=127.0.0.1;dbname=xxx", "xxx", "xxx");
}

public function sqlFetchAssoc($query) {

    $sth = $this->connection->prepare($query);
    $sth->execute();
    $result = $sth->fetchAll(PDO::FETCH_ASSOC);

    return $result;
    }
}

echo "Test started <br><br>";
echo "Initialization: <br>";
$functions = new Functions();
echo "Correct<br><br>";
echo "Performing a select: <br>";
$row = $functions->sqlFetchAssoc("SELECT * FROM chatlogs WHERE id = 70");
print_r($row);
echo "Test finished.";
?>

然后对第一个类做类似的事情。这样不仅会更容易发现错误，而且如果发生错误，您可以通过这些测试来查看出了什么问题，而不用重新编写它们。请记住不要将它们包含在生产代码中。