php - 基于其他行的 PDO 查询过滤器

Question

这是我的代码:

//Connects to Database
    if ($_SERVER["REQUEST_METHOD"] == "POST")
    try
    {
        $dbh = new PDO('dbconnection');
        foreach ($dbh->query('SELECT * from table' ) as $row)
        {
            $instructor = ($_POST["name"]);
            //Loads Certificate Template
            $jpg_image = imagecreatefromjpeg('cert.jpg');
            $color = imagecolorallocate($jpg_image, 82, 122, 124);
            //Sets Font
            $font_path = 'name.ttf';
            //Calls first name from database
            $firstname = $row['fname'];
            //Makes entire first name lower case
            $firstnamelower = strtolower($firstname);
            $firstnameucfirst = ucfirst($firstnamelower);
            //Calls Last Name From Database
            $lastname = $row['lname'];
            $lastnamelower = strtolower($lastname);
            $lastnameucfirst = ucfirst($lastnamelower);
            $name = $firstnameucfirst . ' ' . $lastnameucfirst;
            $font_size = 75;
            imagettftext($jpg_image, $font_size, 0, 810, 530, $color, $font_path, $name);
            imagettftext($jpg_image, 40, 0, 375, 945, $color, $font_path, $instructor);
            imagejpeg($jpg_image, 'images/' . $name . '.jpg', 50);
            imagedestroy($jpg_image);
        }
        $dbh = null;
    }
    catch (PDOException $e)
    {
        print "Error!: " . $e->getMessage() . "<br/>";
        die();
    }
    echo "All certificates have been created."

    ?>

所以我尝试更改它，以便仅处理满足另一个要求的图像。基本上我需要使用 WHERE column_name 运算符值；但当我这样做时，我会遇到错误，我用谷歌搜索了一下，但我不太明白他们在说什么。使用 pdo 完成此操作是否还需要另一段代码？

这是我收到的错误警告:为 foreach() 提供的参数无效

Answer 1

该错误是由于您的 $pdo->query 在失败时返回 false 而不是空数组。

http://www.php.net/manual/en/pdo.query.php

foreach 需要一个数组。

调整您的代码:

$dbh = new PDO('dbconnection');

// Throw exceptions on errors
$dbh->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);

// To make it easier to debug
$sql = 'SELECT * from table';

// To allow check for failuer
$rows = $dbh->execute($sql);

if ($rows === false) ... oopsie

foreach($rows as $row) ...

然后让您的查询发挥作用。考虑直接使用mysql来检查你的sql。