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()。我选择的数据其实就在那里（我查过）。问题是什么？

Connection.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(); 
    } 
    } 
} 

?> 

的functions.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

我发现你在Connection.php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，您可以完全剥离设置$this->something，因为您在相同的功能中使用这些值。这将使它更简单：

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

我建议更进一步。你应该分别测试测试。您可以在testfunction.php写这个剧本并调试它（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."; 
?> 

然后做一流的类似的东西。那么不仅可以更容易地发现错误，而且如果发生错误，您可以参加这些测试，看看出了什么问题，而不是再次写出错误。切记不要将它们包含在生产代码中。