duanbiyi7319 2016-03-26 04:28 采纳率: 100%
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在PHP中的未定义索引

I get an error of Undefined index, what is the reason?

while ($row = mysqli_fetch_array($result)) {
        echo "<tr>";

        echo "<td>" . $row['CandidateName'] . "</td>";
        echo "<td>" . $row['Position'] . "</td>";
         echo "<td><input type='radio' name='candidateid' value='".$row['candidateID']."' >";
      echo "<td>" . $row['NumberofVotes'] . "</td>";
        $candidateid=$row['CandidateID'];

    }

Here is the error

Array ( [0] => 1 [CandidateID] => 1 [1] => Jejomar Binay [CandidateName] => Jejomar Binay [2] => President [Position] => President [3] => [NumberofVotes] => ) Array ( [0] => 2 [CandidateID] => 2 [1] => Mar Roxas [CandidateName] => Mar Roxas [2] => President [Position] => President [3] => 1 [NumberofVotes] => 1 )

I will show you now the whole code and the its working now, my output here is to add 1 in number of votes when the radio button is working. it has no error but when i selected the first radio button it only updates the second data.

<html>
        <center>
        <font size="2" face = "century gothic">
        <?php
        $con=mysqli_connect("localhost","root","","election2016");
        // Check connection
        if (mysqli_connect_errno())
        {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
        }
        $result = mysqli_query($con,"SELECT * FROM candidate_info");
        echo "<table border='1'>
        <tr>
        <th>Candidate Name</th>
        <th>Position</th>
        <th>Vote</th>
        <th>Number of Votes</th>
        </tr>";
        while ($row = mysqli_fetch_array($result)) {
            echo "<tr>";

            echo "<td>" . $row['CandidateName'] . "</td>";
            echo "<td>" . $row['Position'] . "</td>";
             echo "<td><input type='radio' name='candidateid' value='".$row['CandidateID']."' >";
          echo "<td>" . $row['NumberofVotes'] . "</td>";
            $candidateID=$row['CandidateID'];

        }
        echo "</table>";
        mysqli_close($con);
        ?>

        <br>
        <br>
        <form method = "post" action = "<?php $_PHP_SELF ?>">
     <input type="text" name="candidateid" value="<?php echo $candidateID;?>">
         <input name = "update" type = "submit" id = "update" value = "update">
        </form>
        </center>
        </font>
        </html>
        <?php
                 if(isset($_POST['update'])) {
                    $dbhost = 'localhost';
                    $dbuser = 'root';
                    $dbpass = '';
 $candidateid = $_POST['candidateid'];
                    $conn = mysql_connect($dbhost, $dbuser, $dbpass);

                    if(! $conn ) {
                       die('Could not connect: ' . mysql_error());
                    }

                    $candidateid = $_POST['candidateid'];


                    $sql = "UPDATE candidate_info SET numberofvotes = 1 WHERE candidateid = '$candidateid'" ;
                    mysql_select_db('election2016');
                    $retval = mysql_query( $sql, $conn );

                    if(! $retval ) {
                       die('Could not update data: ' . mysql_error());
                    }
                    echo "Updated data successfully
";

                    mysql_close($conn);
                 }
        ?>
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3条回答 默认 最新

  • duankousong9637 2016-03-26 06:48
    关注

    The field "candidateid" should be integer data type, but you are enclosed this field value with ''(single quotes) in the update query?

    $sql = "UPDATE candidate_info SET numberofvotes = 1 WHERE candidateid = '$candidateid'";
    

    if it is an integer datatype then you should remove the single quote

    $sql = "UPDATE candidate_info SET numberofvotes = 1 WHERE candidateid = $candidateid";
    

    and in MySQL every field names are case sensitive, so as you told the field names are

    candidateid, candidatename, position, numberofvotes

    so, you should use these names when you retrieving the values as well

        <?php
                 if(isset($_POST['update'])) {
                    $dbhost = 'localhost';
                    $dbuser = 'root';
                    $dbpass = '';
                    $candidateid = $_POST['candidateid'];
                    $conn = mysql_connect($dbhost, $dbuser, $dbpass);
    
                    if(! $conn ) {
                       die('Could not connect: ' . mysql_error());
                    }
    
                    $candidateid = $_POST['candidateid'];
    
    
                    $sql = "UPDATE candidate_info SET numberofvotes = numberofvotes + 1 WHERE candidateid = '$candidateid'" ;
                    mysql_select_db('election2016');
                    $retval = mysql_query( $sql, $conn );
    
                    if(! $retval ) {
                       die('Could not update data: ' . mysql_error());
                    }
                    echo "Updated data successfully
    ";
    
                    mysql_close($conn);
                 }
        ?>
    <html>
        <center>
        <font size="2" face = "century gothic">
        <?php
        $con=mysqli_connect("localhost","root","","election2016");
        // Check connection
        if (mysqli_connect_errno())
        {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
        }
        $result = mysqli_query($con,"SELECT * FROM candidate_info");
        ?>
        <form method = "post" action = "<?php $_PHP_SELF ?>">
        <?php
        echo "<table border='1'>
        <tr>
        <th>Candidate Name</th>
        <th>Position</th>
        <th>Vote</th>
        <th>Number of Votes</th>
        </tr>";
        while ($row = mysqli_fetch_array($result)) {
            echo "<tr>";
            echo "<td>" . $row['candidatename'] . "</td>";
            echo "<td>" . $row['position'] . "</td>";
            echo "<td><input type='radio' name='candidateid' value='".$row['candidateid']."' >";
            echo "<td>" . $row['numberofvotes'] . "</td>";
        }
        echo "</table>";
        mysqli_close($con);
        ?>
    
        <br>
        <br>
        <input name = "update" type = "submit" id = "update" value = "update">
        </form>
        </center>
        </font>
        </html>
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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