PHP检查是否查询远程数据库返回的数据使用PDO

Question

下面的代码用于检查某个查询是否返回数据。该查询获取用户在另一个页面上搜索的会话数据。

$whatwechecking = $_SESSION ['assignment_searched']; 

$FindAsigns = $connection->query("SELECT `NAME`,`DATE`,`GRADE` FROM grades 
WHERE `ASSIGNMENT` = '$whatwechecking' ORDER BY `ASSIGN_ID` DESC LIMIT 0,5");
if ($FindAsigns->fetchColumn() > 0) //this is the attempt at seeing if 
                                  //the query returned something
{
while($row = $FindAssigns->fetch()) //this loop outputs the data found in the 
                                    //query into a table
 {
    ...find data

    echo (...echo out data into table);

}
    }
    else
    {
        header('Location: NameNotFound.php'); //this is to redirect the user
                    to an error page that says data was not retreived in the query
    }

理想情况下，我想在PDO中这样做，因为查询是在相同的标准。我认为在这种情况下，获取行方法不是最理想的，那么是否有更好的方法来查看查询是否没有返回任何内容?

Answer 1

有几点。当前查询不是sql安全的。$_SESSION['assignment_searched']可能包含恶意值，因此我建议使用PDO Quote函数或使用准备好的语句。在下面的例子中，我使用了预处理语句。

一旦你准备好并执行了查询，你就可以很容易地检查返回了多少行并循环它们。

在互联网上有很多有用的PDO的例子。在谷歌上快速搜索一下会有帮助。关于PDO的PHP手册也非常好，社区贡献了许多示例。 https://www.google.com/search?q=PHP

+ PDO + MySQL +例子http://www.php.net/manual/en/book.pdo.php

// Create PDO Prepared Statement (leave placeholder for our variable)
$stmt = $connection->prepare("
    SELECT `NAME`, `DATE`, `GRADE` FROM grades
    WHERE `ASSIGNMENT` = :whatwechecking
    ORDER BY `ASSIGN_ID` DESC
    LIMIT 0,5
");
// Bind Data to Placeholder in Statement and Execute (SQL-safe)
$stmt->execute(array('whatwechecking' => $_SESSION['assignment_searched']));
// Check if Anything was returned
if ($stmt->rowCount() > 0) { 
    // YES! Fetch Items and Loop Through
    foreach ($stmt->fetchAll() as $item) {
        var_dump($item);
    }
}