准备好的语句错误

Question

在调试过程中，我注意到脚本死于$stmt->fetch() or die($stmt->error);行。 PHP日志中没有错误。它也不回应任何错误。你在代码中看到任何错误的东西吗？

$stmt = $db->prepare("SELECT e.msg_subject AS subject, e.msg_text AS text, u.fname AS firstname, u.lname AS lastname FROM emails AS e, users AS u WHERE e.msg_status=? AND e.msg_type=? AND u.id=?") or die($db->error); 
    $stmt->bind_param("isi", $status, $type, $userid) or die($stmt->error); 
    $stmt->execute() or die($stmt->error); 
    $stmt->bind_result($subject, $text, $firstname, $lastname) or die($stmt->error); 
    $stmt->fetch() or die($stmt->error); 
    $stmt->close(); 

Answer 1

的问题是，$stmt->fetch()返回布尔FALSE如果没有行通过SQL语句检索。所以，你必须检查行数：

if ($stmt->num_rows > 0) { 
    $stmt->fetch() or die($stmt->error); 
}