Question

在我的本地xampp上运行while脚本时，它只是一遍又一遍地返回相同的结果，这是我正在使用的PHP：

<?php
$id = $_GET['id'];
$getmembers = mysql_query("SELECT * FROM group_memberships WHERE groupid = $id LIMIT 10");
$getids = mysql_fetch_assoc($getmembers);
    while($id = $getids['userid']){
        $getusers = mysql_fetch_assoc(mysql_query("SELECT look, username FROM users WHERE id = '$id'"));
        echo ($getusers['username']);
        echo('<br />');
    }
?>

我执行的所有操作都是：http://prntscr.com/12nh6g我的数据库包含4个注册到该组的不同用户。我不确定在MySQL中加入表格，因为我不知道该怎么做。

如果我加一个休息时间;然后它只返回一个结果，而不是超时。

非常感谢任何帮助！

此外，我很抱歉PHP是多么混乱，我是新手。

Answer 1

while($id = $getids['userid']){ #This condition will always be true.

在下面的循环中使用您的mysql_fetch_assoc语句。

while ($getids = mysql_fetch_assoc($getmembers)) {
    $id = $getids['userid']
    $getusers = mysql_fetch_assoc(mysql_query("SELECT look, username FROM users WHERE id = '$id'"));
    echo $getusers['username'];
    echo '<br />';
}

对于子查询，您可以尝试

SELECT look, username FROM users
WHERE id IN 
       (SELECT userId FROM group_memberships
        WHERE groupid = $id
        LIMIT 10)

使用加入，

SELECT u.look,u.username
FROM users as u
LEFT JOIN group_memberships as gm
     on gm.userId = u.id 
     WHERE gm.groupid = $id
     LIMIT 10

注意： Please, don't use mysql_* functions in new code。它们不再被维护and are officially deprecated。请参阅red box？转而了解prepared statements，并使用PDO或MySQLi - this article将帮助您确定哪个。如果您选择PDO here is a good tutorial。

Answer 2

<?php

$id = (int) $_GET['id']; // very important part here, I cast the id to int, else you have a SQL injection leak
$getmembers = mysql_query("SELECT * FROM group_memberships WHERE groupid = $id LIMIT 10");
while ($membership = mysql_fetch_assoc($getmembers)) // on each pass we take a new result off first query
{
    $user = mysql_fetch_assoc(mysql_query("SELECT look, username FROM users WHERE id = '".$membership['user_id']."'"));
    echo ($user['username']);
    echo('<br />');
}
?>

Answer 3

在您的代码中：

<?php
$id = $_GET['id'];
$getmembers = mysql_query("SELECT * FROM group_memberships WHERE groupid = $id LIMIT 10");
$getids = mysql_fetch_assoc($getmembers);
    while($id = $getids['userid']){
        $getusers = mysql_fetch_assoc(mysql_query("SELECT look, username FROM users WHERE id = '$id'"));
        echo ($getusers['username']);
        echo('<br />');
    }
?>

告诉PHP “做循环”，而$ id被分配给$ getids ['userid']的值

因此，您将拥有一个无限循环，因为$ id一直被分配（并且始终具有相同的值）$ getids永远不会在while循环中更改。

但即使$ getids即将改变它仍然会处于无限循环中，因为循环不检查$ getids ['userid'] 的$ id是否值，它只是分配值。

Answer 4

<?php
$id = $_GET['id'];
$getmembers = mysql_query("SELECT * FROM group_memberships WHERE groupid = $id LIMIT 10");

    while($getids = mysql_fetch_assoc($getmembers)){
    $getusers = mysql_fetch_assoc(mysql_query("SELECT look, username FROM users WHERE id = '$id'"));
    echo ($getusers['username']);
    echo('<br />');
    }
?>

你的while循环错了，你需要在循环中进行内移，所以直到取出停止。

PHP重复返回相同的结果

4 个答案: