SQL错误：mysqli_stmt :: bind_param（）：类型定义字符串中的元素数量与绑定变量的数量不匹配

Question

我有以下代码：

$conn = new mysqli($DB, $username, $password, $dbname); 

if($condition == 'con1'){
    $sql = "UPDATE users SET con1=? WHERE name=?";  
}elseif($condition == 'con2'){
    $sql = "UPDATE users SET con2=? WHERE name=?";  
}elseif($condition == 'con3'){
    $sql = "UPDATE users SET con3=? WHERE name=?";  
}

if($query = $conn->prepare($sql)) { 
    $query->bind_param($value,$name);
    $query->execute();

    print_r($query);

} else {
    $error = $conn->errno . ' ' . $conn->error;
    echo $error; 
}

然后我得到那个错误：

Warning:  mysqli_stmt::bind_param(): Number of elements in type definition string doesn't match number of bind variables on line 32

这就是从$query打印出来的内容：

mysqli_stmt Object
(
[affected_rows] => -1
[insert_id] => 0
[num_rows] => 0
[param_count] => 2
[field_count] => 0
[errno] => 2031
[error] => No data supplied for parameters in prepared statement
[error_list] => Array
    (
        [0] => Array
            (
                [errno] => 2031
                [sqlstate] => HY000
                [error] => No data supplied for parameters in prepared statement
            )

    )

[sqlstate] => HY000
[id] => 1
)

有2个 ？ ，以及2个变量，但我收到错误消息，指出参数数量不等于变量数量。

问题是什么？

Answer 1

就您的情况而言，是您不正确地使用-> bind_param函数。

// prepare and bind
$stmt = $conn->prepare("INSERT INTO MyGuests (firstname, lastname, email) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $firstname, $lastname, $email); // sss means string string string

// set parameters and execute
$firstname = "John";
$lastname = "Doe";
$email = "john@example.com";
$stmt->execute();

该参数可能是以下四种类型之一：

• i-整数
• d-双倍
• s-字符串
• b-BLOB

我相信正确的代码应如下所示：

$conn = new mysqli($DB, $username, $password, $dbname); 

// You can avoid this structure, by doing concatenation!!!**
if($condition == 'con1'){
    $sql = "UPDATE users SET con1=? WHERE name=?";  
}elseif($condition == 'con2'){
    $sql = "UPDATE users SET con2=? WHERE name=?";  
}elseif($condition == 'con3'){
    $sql = "UPDATE users SET con3=? WHERE name=?";  
}

if($query = $conn->prepare($sql)) { 
    $query->bind_param("ss", $con, $name);
    $con = 'yourNeededValue';
    $name = 'someName?';
    $query->execute();

} else {
    $error = $conn->errno . ' ' . $conn->error;
    echo $error; 
}