Question

遇到问题，如果行等于0，则不调用else语句。如果我在网站上输入正确的详细信息，则会满足第一个条件并显示xml，但是如果输入了错误的详细信息，则不会显示错误xml。

echo "<users>"; 
$result = mysql_query("SELECT * FROM `numbers` WHERE `email` = '".$email."' AND `password` = '".$password."'") or die('Invalid query: ' . mysql_error());

if (!$result) die('Invalid query: ' . mysql_error());
while ($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
    if(mysql_num_rows($result) != 0)
    {
        echo "<usercallback>";
        echo  "<id>".$row['id']."</id>";
        //echo  "<number>".$row2['number']."</number>";
        //echo  "<gender>".$row2['gender']."</gender>";
        //echo  "<relationship>".$row2['relationship']."</relationship>";
        echo  "</usercallback>";
    }
    else
    {
        echo "<usercallback>";
        echo  "<id>error</id>";
        echo  "</usercallback>";
    }
}

echo "</users>";

Answer 1

实际上你必须将if mysql_num_rows检查放在while块

之外

echo "<users>"; 
$result = mysql_query("SELECT * FROM `numbers` WHERE `email` = '".$email."' AND `password` = '".$password."'") or die('Invalid query: ' . mysql_error());


if(mysql_num_rows($result) != 0)
    {
    while ($row = mysql_fetch_array($result, MYSQL_ASSOC))
        {       
        echo "<usercallback>";
        echo  "<id>".$row['id']."</id>";
        //echo  "<number>".$row2['number']."</number>";
        //echo  "<gender>".$row2['gender']."</gender>";
        //echo  "<relationship>".$row2['relationship']."</relationship>";
        echo  "</usercallback>";
        }
    }
    else
    {
        echo "<usercallback>";
        echo  "<id>error</id>";
        echo  "</usercallback>";
    }

echo "</users>";

Answer 2

while ($row = mysql_fetch_array($result, MYSQL_ASSOC))

如果没有行，那么$row将为false，并且它永远不会进入上面的while循环。所以你不能得到错误信息

Answer 3

在执行循环时检查行，您应该检查while循环之前的行数。

Answer 4

看起来你期待MySQL的零行响应导致undef $结果。这不是发生的事情。如果出现错误，mysql_query()将返回null。您可以测试其返回值的“真实性”，以查看查询是否正确运行。如果查询导致0行响应，则正确运行。要测试的值是mysql_num_rows($result)。

然而，它可以更简单。我通常这样写：

$res = mysql_query("SELECT 1");
if (!$res) {
    //do whatever error reporting if the SQL was bad
    //though you should probably deal with any condition that ends up
    //here before you go into production!
}
if (mysql_num_rows($res) == 0) {
    //put out my "no results found" message
}
while ($row = mysql_fetch_assoc($res)) {
    //do my per-row business
}

当没有（或没有）结果返回时，

mysql_fetch_assoc()返回false。因此，如果它为空，则while循环将永远不会运行，因此它不需要位于else内。

PHP Mysql If语句不起作用

4 个答案: