mysqli代码和call_user_func_array()中出现的错误

Question

尝试使用mysqli创建动态where子句时,我遇到了很多错误:

警告:参数2到mysqli_stmt :: bind_param()应该是一个引用,在第319行的......中给出的值

警告:mysqli_stmt :: execute():( HY000/2031):没有为第328行的...中的预准备语句中的参数提供数据

警告:mysqli_stmt :: bind_result():( HY000/2031):没有为第331行的...中的预准备语句中的参数提供数据

警告:mysqli_stmt :: store_result():( HY000/2014):命令不同步; 您现在无法在第332行的...中运行此命令

我猜测解决问题需要一点点改变,但是如果两个下拉菜单中的一个不相等All或两者不相等All那么它就会出现错误.

下面是代码显示下拉菜单和后面的查询(带有动态where子句),具体取决于所选的n个选项:

HTML:

学生下拉菜单:

<select name="student" id="studentsDrop">
<option value="All">All</option>
<option value="11">John May</option>
<option value="23">Chris Park</option>
</select>

问题编号下拉菜单

<select name="question" id="questionsDrop">
<option value="All">All</option>
<option value="123">1</option>
<option value="124">2</option>
<option value="125">3</option>
</select>

PHP /库MySQLi:

      function StudentAnswers()
        {


    /*BELOW IS THE QUERY WHERE I AM TRYING TO RETRIEVE DATA DEPENDING ON THE ASSESSMENT CHOSEN AND
    THEN DEPENDING ON OPTIONS CHOSEN IN STUDENT AND QUESTION NUMBER DROP DOWN MENU */

        $selectedstudentanswerqry = "
        SELECT
        StudentAlias, StudentForename, StudentSurname, q.SessionId, QuestionNo, QuestionContent, o.OptionType, q.NoofAnswers, GROUP_CONCAT( DISTINCT Answer
        ORDER BY Answer SEPARATOR ',' ) AS Answer, r.ReplyType, QuestionMarks, 
        GROUP_CONCAT(DISTINCT StudentAnswer ORDER BY StudentAnswer SEPARATOR ',') AS StudentAnswer, ResponseTime, MouseClick, StudentMark
        FROM Student s
        INNER JOIN Student_Answer sa ON (s.StudentId = sa.StudentId)
        INNER JOIN Student_Response sr ON (sa.StudentId = sr.StudentId)
        INNER JOIN Question q ON (sa.QuestionId = q.QuestionId)
        INNER JOIN Answer an ON q.QuestionId = an.QuestionId
        LEFT JOIN Reply r ON q.ReplyId = r.ReplyId
        LEFT JOIN Option_Table o ON q.OptionId = o.OptionId
        ";

        // Initially empty
        $where = array('q.SessionId = ?');
        $parameters = array($_POST["session"]);
        $parameterTypes = 'i';

        // Check whether a specific student was selected
        if($_POST["student"] !== 'All') {
            $where[] = 'sa.StudentId = ?';
            $parameters[] =& $_POST["student"];
            $parameterTypes .= 'i';
        }

        // Check whether a specific question was selected
        // NB: This is not an else if!
        if($_POST["question"] !== 'All') {
            $where[] = 'q.QuestionId = ?';
            $parameters[] =& $_POST["question"];
            $parameterTypes .= 'i';
        }

        // If we added to $where in any of the conditionals, we need a WHERE clause in
        // our query
        if(!empty($where)) {
            $selectedstudentanswerqry .= ' WHERE ' . implode(' AND ', $where);
            global $mysqli;
            $selectedstudentanswerstmt=$mysqli->prepare($selectedstudentanswerqry);
            // You only need to call bind_param once
                call_user_func_array(array($selectedstudentanswerstmt, 'bind_param'),
                array_merge(array($parameterTypes), $parameters)); //LINE 319 ERROR 1
        }

    //Add group by and order by clause to query
        $selectedstudentanswerqry .= "
          GROUP BY sa.StudentId, q.QuestionId
          ORDER BY StudentAlias, q.SessionId, QuestionNo
        ";

        // get result and assign variables (prefix with db)
        $selectedstudentanswerstmt->execute(); //LINE 328 ERROR 2

    //bind database fields 
$selectedstudentanswerstmt->bind_result($detailsStudentAlias,$detailsStudentForename,$detailsStudentSurname,$detailsSessionId,$detailsQuestionNo, 
        $detailsQuestonContent,$detailsOptionType,$detailsNoofAnswers,$detailsAnswer,$detailsReplyType,$detailsQuestionMarks,$detailsStudentAnswer,$detailsResponseTime,
        $detailsMouseClick,$detailsStudentMark); //LINE 331 ERROR 3

    //store results retrieved
        $selectedstudentanswerstmt->store_result(); //LINE 332 ERROR 4

    //count number of rows retrieved
        $selectedstudentanswernum = $selectedstudentanswerstmt->num_rows();     

    //output query
        echo "$selectedstudentanswerqry";

        }

        ?>

这是一个DEMO: DEMO

在演示中,从下拉菜单中选择评估并提交.您将看到两个下拉菜单.保持它们都设置为All并提交,它将输出查询没有问题.在其中一个下拉菜单中没有,请更改All为特定的学生或问题,然后提交.现在您将看到错误

VAR DUMP:

var_dump(array_merge(array($parameterTypes), $parameters)));我选择会话(评估)时的结果,包括值31,学号40和价值,以及81WHERE CLAUSE WHERE q.SessionId = ? AND sa.StudentId = ? AND q.QuestionId = ?:

我得到这个输出: array(4) { [0]=> string(3) "iii" [1]=> string(2) "31" [2]=> string(2) "40" [3]=> string(2) "81" }

Answer 1

这是一个棘手的情况，是由 PHP 5.4 中的行为变化引起的call_user_func_array（我必须假设）：文档

尽管这很丑陋，但可以bind_param这样调用：

$selectedstudentanswerqry .= ' WHERE ' . implode(' AND ', $where);
global $mysqli;
$stmt =$mysqli->prepare($selectedstudentanswerqry);

if (count($where) === 1) {
    $stmt->bind_param($parameterTypes, $parameters[0]);
}
else if (count($where) === 2) {
    $stmt->bind_param($parameterTypes, $parameters[0], $parameters[1]);
}
else if (count($where) === 3) {
    $stmt->bind_param($parameterTypes, $parameters[0], $parameters[1],
       $parameters[2]);
}

我和你一样讨厌这个。我建议切换到mysqli以PDO更好的方式处理变量参数（在我看来，通常具有优越的语法）：

$pdo = new PDO('mysql:host=localhost', 'username', 'password');
$stmt = $pdo->prepare($selectedstudentanswerqry);
$stmt->execute($parameters);
$selectedstudentanswernum = $stmt->rowCount();