Php 无法从表单标记更新MYsql数据库上的数据

在将数据更新到mySQL数据库时遇到问题。我很好地连接到数据库，可以很好地提取信息，但为什么它不发送信息并存储呢？下面是php，如果用户想要修改这些数据

 <?php
 if(isset($_POST['Modify']))
 {
   if(!empty($_REQUEST['rep_num']))
   {
     print "Nothing was entered."   ;
   } else {
        $rep_num=$row['REP_NUM'];
        $last_name=$row['LAST_NAME'];
        $first_name=$row['FIRST_NAME'];
        $street=$row['STREET'];
        $city=$row['CITY'];
        $state=$row['STATE'];
        $zip=$row['ZIP'];
        $commission=$row['COMMISSION'];
        $rate=$row['RATE'];
        $error = 0;

        // if($rep_num == NULL ||
        //     $last_name==NULL||
        //     $first_name==NULL||
        //     $street==NULL||
        //     $city==NULL||
        //     $state==NULL||
        //     $zip==NULL||
        //     $commission==NULL||
        //     $rate==NULL)
        // {
        //     print "All fields must be completed in order to carry on!";
        //     $error++;
        // }
        if(empty($_REQUEST['rep_num']) || empty($_REQUEST['last_name']) || empty($_REQUEST['first_name']) || empty($_REQUEST['street']) || empty($_REQUEST['city']) || empty($_REQUEST['state']) || empty($_REQUEST['zip']) || empty($_REQUEST['commission']) || empty($_REQUEST['rate']))
        {
            print "There is information missing from your form.";
        }
        if(!is_numeric($zip)&&$zip!=NULL)
        {
            print "Invalid Zip Code";
            $error++;                   
        }

        $state_length = strlen($state);

        if(($state_length != 2 || is_numeric($state))&&$state!=NULL)
        {
            print "Invalid State";
            $error++;                                                   
        }

        // if ($error != 0)
        // {
        //     echo "<p>The data for Sales Representative ".$num." is displayed below</p>";
        // }

        elseif($error==0)
        {
            $new_state = strtoupper($state);

            $query = mysql_query("UPDATE REP SET REP_NUM ='$rep_num', FIRST_NAME = '$first_name', LAST_NAME ='$last_name', STREET ='$street', CITY ='$city', STATE ='$new_state', ZIP ='$zip', COMMISSION = '$commission', RATE = '$rate' WHERE REP_NUM='$rep_num'");
            $viewquery= "SELECT * FROM REP WHERE REP_NUM = '$rep_num'";

            if($r=mysql_query($viewquery))
            {
                echo "<center>";
                    echo "<table border = '2' cellpadding = '5' style='font-size: 12px; border-color: white; border-style: outset; padding: 5px; text-align:center'>
                        <tr bgcolor='gray'>
                        <th>Sales Rep Number</th>
                        <th>Sales Rep Full Name</th>
                        <th>Street</th>
                        <th>City</th>
                        <th>State</th>
                        <th>Zip</th>
                        <th>Commission</th>
                        <th>Rate</th>
                        </tr>";
                            $row=mysql_fetch_array($r);
                            echo"<p>Modification successful. <br />The modified data for Sales Representative number ".$row['REP_NUM']." is displayed below.</p>";
                            echo"<tr>";
                       echo"<td>" .$row['REP_NUM'] ."</td>";
                        echo"<td>" .$row['LAST_NAME'] ."</td>";
                        echo"<td>" .$row['STREET'] ."</td>";
                        echo"<td>" .$row['CITY'] ."</td>";
                        echo"<td>" .$row['STATE'] ."</td>";
                        echo"<td>" .$row['ZIP'] ."</td>";
                        echo"<td>" .$row['COMMISSION'] ."</td>";
                        echo"<td>" .$row['RATE'] ."</td>";
                        echo"</tr>";
                    echo "</table>";
                echo"</center>";
                echo"<br /><br />";
            }
        }
    }
}
?>

---

$row
是否已定义？或者应该是
\u POST
？错误报告正在进行吗？也可以在这里进行SQL注入，并应将驱动程序更新为
pdo
或
mysqli
$viewquery=mysql\u query（“从REP中选择*，其中REP\u NUM='$REP\u NUM'）；如果（$row=mysql_fetch_array（$viewquery））{必须从$row更改为_POST