Question

我遇到了最简单的代码问题。出于某种原因，以下代码仅检索数据库的第一行。我正在尝试一个循环，它只是不适合我。这是我的代码：

<?php


//Connect to the database
require_once('mysql_connect.php') ;

$query = "SELECT * FROM past_due_students WHERE charged_today = 'No' ORDER BY past_due_id" ;
$result = mysqli_query($dbc, $query) ;
$number_of_students = mysqli_num_rows($result) 

if ($number_of_students >= 1) {

    //Loop through the entire table
    while ($row = mysqli_fetch_array($result, MYSQLI_BOTH)) {

        $student_id = $row['student_id'] ;
        $number_of_declines = $row['number_of_declines'] - 1;

        //Update the number of declines
        $query = "UPDATE past_due_students SET number_of_declines = $number_of_declines WHERE student_id = $student_id" ;
        $result = mysqli_query($dbc, $query) ;
        $number = mysqli_affected_rows($dbc) ;

        if ($number == 1) {

            echo '<p><b>The number of declines has been successfully updated.</b></p>' ;

        } else {
            echo $query ;
        }

    }//END while loop

}//END if ($number_of_students >= 1) {

?>

它只抓取第一行而没有其他行。

Answer 1

您正在覆盖$result：

的值

$query = "SELECT * FROM past_due_students....." ;
$result = mysqli_query($dbc, $query) ;

//Loop through the entire table
 while ($row = mysqli_fetch_array($result, MYSQLI_BOTH)) {

    $query = "UPDATE past_due_students SET  ...." ;
    $result = mysqli_query($dbc, $query) ; <-- OVERWRITTING HERE.

使用其他变量来保存内部查询结果对象。

Answer 2

通过将下一个查询资源分配给同一个变量，您正在销毁从SELECT查询中获得的$result资源。

请为UPDATE查询使用其他变量。

所以改变这个：

$query = "UPDATE past_due_students SET number_of_declines = $number_of_declines WHERE student_id = $student_id" ;
$result = mysqli_query($dbc, $query) ;

对此：

$query = "UPDATE past_due_students SET number_of_declines = $number_of_declines WHERE student_id = $student_id" ;
$updateResult = mysqli_query($dbc, $query) ;

Answer 3

尝试使用其他变量名称

更改$ update的更新结果

Answer 4

你正在覆盖你的循环中的$result var。您的第二个mysqli_affected_rows也正在传递数据库对象。

更改

$result = mysqli_query($dbc, $query) ;
$number = mysqli_affected_rows($dbc) ;

到

$result2 = mysqli_query($dbc, $query) ;
$number = mysqli_affected_rows($result2) ;

如何在PHP中使用While循环？

4 个答案: