Question

修改

我现在收到错误：

  Warning: mysql_num_rows() expects parameter 1 to be resource, null given in /home/jahedhus/public_html/system/vote.php on line 126

我的php代码如下：

    <?php 

$id = $_GET['election'];

$result = mysql_query("SELECT * FROM votes WHERE election_id = '$id' AND ni = '". $_SESSION['ni']."'" )

or die(mysql_error());

if (mysql_num_rows($result) == 0) {

   $sql="SELECT * FROM elections WHERE status = 'in_progress' AND election_id = '$id'";

$result1=mysql_query($sql);

$options="";
$party2="";
$party3="";

while ($row=mysql_fetch_array($result1)) {

    echo "<tr>";
    echo "<td><h5>" . $row['name_of_election']. "</h5><hr></td>";
    echo "</td>";


    $idd=$row["party1"];
    $thing=$row["party1"];
    $options.="<OPTION VALUE=\"$idd\">".$thing;

    $idd=$row["party2"];
    $thing=$row["party2"];
    $party2.="<OPTION VALUE=\"$idd\">".$thing; 

    $idd=$row["party3"];
    $thing=$row["party3"];
    $party3.="<OPTION VALUE=\"$idd\">".$thing;

}
}
?>

<?php if (mysql_num_rows($result1) == 0) : ?>
  <form action="votecasted.php?election=<?php echo $id; ?>" method="post">

    <span id="spryselect1">
    <label for="vote">Vote</label>&nbsp;
    <select size=1" name="vote" id="vote">
        <option selected="selected">Select Your Desired Party</option>
        <?=$options?>
        <?=$party2?>
        <?=$party3?>
</select>
    <span class="selectRequiredMsg">*</span></span><br />

<br />    <input name="" type="submit" value="Vote" />
  </form>

<?php else : ?>
    You cannot post vote anymore.
<?php endif; ?>

第126行是：

<?php if (mysql_num_rows($result1) == 0) : ?>

一旦用户投票，这很奇怪，它会显示错误消息，如果用户没有投票，则显示“你不能再投票了。”

Answer 1

如果我正确理解了这个问题，您只需检查$result是否与false不同。我建议您对嵌入式PHP使用以下语法：

<?php if ($result) : ?>
    <form></form>
<?php else : ?>
    Something else
<?php endif; ?>

在您的情况下，再进行一些SQL注入检查：

<?php 
$id = mysql_real_escape_string($_GET['election']);
$ni = mysql_real_escape_string($_SESSION['ni']);
$votes = mysql_query("SELECT * FROM votes WHERE election_id = '$id' AND ni = '$ni'" )
or die(mysql_error());

if (mysql_num_rows($votes) == 0) {
    $sql = "SELECT * FROM elections WHERE status = 'in_progress' AND election_id = '$id'";
    $elections = mysql_query($sql);

    $options="";
    $party2="";
    $party3="";
    while ($row = mysql_fetch_array($elections)) {
        echo "<tr>";
        echo "<td><h5>" . $row['name_of_election']. "</h5><hr></td>";
        echo "</td>";
        $idd=$row["party1"];
        $thing=$row["party1"];
        $options.="<OPTION VALUE=\"$idd\">".$thing;

        $idd=$row["party2"];
        $thing=$row["party2"];
        $party2.="<OPTION VALUE=\"$idd\">".$thing; 

        $idd=$row["party3"];
        $thing=$row["party3"];
        $party3.="<OPTION VALUE=\"$idd\">".$thing;
    }
}
?>

<?php if (mysql_num_rows($votes) == 0) : ?>
    <form action="votecasted.php?election=<?=$id?>" method="post">
        <span id="spryselect1">
        <label for="vote">Vote</label>&nbsp;
        <select size="1" name="vote" id="vote">
            <option selected="selected">Select Your Desired Party</option>
            <?=$options?>
            <?=$party2?>
            <?=$party3?>
        </select>
        <span class="selectRequiredMsg">*</span></span><br />
        <br />
        <input name="" type="submit" value="Vote" />
  </form>
<?php else : ?>
    You cannot post vote anymore.
<?php endif; ?>

我如何说这个陈述是如何呈现然后显示其他如何显示

修改

1 个答案: