Question

有一个问题，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，则满足第一个条件并显示xml，但是如果输入了不正确的详细信息，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

其实你必须把是否mysql_num_rows检查，而块外

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，然后$row将false，它永远不会进入的上方，而循环。 所以你不能得到错误信息

Answer 3

你在执行循环时检查行，你应该检查while循环的行数。

Answer 4

它看起来像你期待MySQL的零行响应导致undef $结果。这不是发生了什么。如果出现错误，mysql_query()返回null。您可以测试其返回值的“真值”以查看查询是否正确运行。如果查询结果为0行响应，则它正确运行。那么测试的值是mysql_num_rows($result)。

但是，它可以做得更简单。我平时写，如：

$res = mysql_query("SELECT 1"); 
if (!$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 
} 

mysql_fetch_assoc()返回false当没有（或没有更多）的成绩来回报。所以如果它是空的，while循环将永远不会运行，所以它不需要在else之内。