MySQL UPDATE查询网页中的错误

Question

My UPDATE query is failing although the syntax looks fine to me (I have another update query that works fine on the same page).

mysql_connect("localhost", "root", "") or die(mysql_error());
mysql_select_db("sitename") or die(mysql_error());

$id = $_GET['id'];

if (isset($_POST['submit'])){                           

        $b = mysql_real_escape_string(trim($_POST['body']));

        //**You have an error in your SQL syntax;** --> ?
        mysql_query ("UPDATE body SET body= $b WHERE id = $id") or die (mysql_error() );

        // $b is fine 
        echo "$b";          

    }

How the HTML review forms are rendered..

// Puts SQL Data into an array
$q = mysql_query("SELECT * FROM vote") or die (mysql_error());

// Now we loop through the database
echo "<br />";
while ($ratings = mysql_fetch_array($q))
{
    //This outputs the doctors's name
    echo "Doctor's name:" . $ratings['doctor_name'] ."<br />";

        //This outputs a textarea for the user to submit comments
        echo "<b>Your Experience: </b>";
        echo "<form method='post' action='review_doctors.php'> 

                <textarea name='body'></textarea>
                <input type='submit' name='submit' value='Send' id='submit'/>
             </form>
             "; 
        echo "<br />";

echo "<p> </p>";
}

Why am I getting a SQL syntax error whenever a comment is submitted?

Answer 1

I fixed it to this:

// If submitted 
if (isset($_POST['id'])){       

            //Capture what was typed in textarea
            $b = mysql_real_escape_string(trim($_POST['body']));

            $id = $_POST['id'];
            mysql_query ("UPDATE vote SET body = '$b' WHERE id = $id") or die (mysql_error() );

            // $b and $id are still fine 
            echo "$b";  
            echo "$id";

        }

Also fixed the hidden input value:

while ($ratings = mysql_fetch_array($q))
{
    //This outputs the doctors's name
    echo "Doctor's name:" . $ratings['doctor_name'] ."<br />";

        $id = $_POST['id'];    

        //This outputs a textarea for the user to submit comments
        echo "<b>Your Experience: </b>";
        echo "<form method='post' action='review_doctors.php'> 

                <textarea name='body'></textarea>
                <input type='submit' name='submit' value='Send'/>


                <input type='hidden' name='id' value='$ratings[id]' />

             </form>
             ";

        echo "<br />";