根据用户操作更新表

Im tryng to update a table based on a user action please help, When i submit the query nothng happens if user selects edit it should update the table what Am I doing wrong?

if ($action == "edit"){


$edit = $_POST['edit'];
$first_name = $_POST['first_name'];
$last_name = $_POST['last_name'];
$email = $_POST['email'];


$sql=mysql_query("select * from user where id='$id'");

   while ($row=mysql_fetch_array($sql)) 
 {                                                                                                                                                                                                                                                     
$id = $row['id'];
$first_name = $row['first_name'];
$last_name = $row['last_name'];
$email = $row['email'];

$result=mysql_query("UPDATE user SET first_name='$first_name',last_name='$last_name',email='$email' WHERE id='$id'");


echo("<form name='edit' method='post' action='?action=edit'>");
echo("<input type='hidden' name='?action=edit'>");
echo("<table class=main cellspacing=0 cellpadding=5 >");
echo("<tr><td>Name: </td><td align='right'><input type='text' name='first_name' value='$first_name'></td></tr>");
echo("<tr><td>Surname: </td><td align='right'><input type='text'  name='last_name' value='$last_name'></td></tr>");
echo("<tr><td>Email: </td><td align='right'><input type='text' name='email' value='$email'></td></tr>");
echo("<tr><td></td><td><div align='right'><input type='submit'></div></td></tr>");
echo("</table>");
     }    
         }

You are updating your database with the results that you are pulling in.

You need to update the database before you select your row:

Couple of notes: You are not setting id in your form (possibly make it a hidden input). The largest problem that I'm seeing is that you aren't initially setting ID (ie when there is no $_POST data).

Additionallly, you should be using PDO or mysqli

if($_POST){
    $id = $_POST['id'];
    $edit = $_POST['edit'];
    $first_name = $_POST['first_name'];
    $last_name = $_POST['last_name'];
    $email = $_POST['email'];
    $result=mysql_query("UPDATE user SET first_name='$first_name',last_name='$last_name',email='$email' WHERE id='$id'");
}

$sql=mysql_query("select * from user where id='$id'");

while ($row=mysql_fetch_array($sql)){                                             
    $id = $row['id'];
    $first_name = $row['first_name'];
    $last_name = $row['last_name'];
    $email = $row['email'];


    echo("<form name='edit' method='post' action='?action=edit'>");
    echo("<input type='hidden' name='?action=edit'>");
    echo("<table class=main cellspacing=0 cellpadding=5 >");
    echo("<tr><td>Name: </td><td align='right'><input type='text' name='first_name' value='$first_name'></td></tr>");
    echo("<tr><td>Surname: </td><td align='right'><input type='text'  name='last_name' value='$last_name'></td></tr>");
    echo("<tr><td>Email: </td><td align='right'><input type='text' name='email' value='$email'></td></tr>");
    echo("<tr><td></td><td><div align='right'><input type='submit'></div></td></tr>");
    echo("</table>");
}

you should check wether the form is sent by the user

if ($_SERVER['REQUEST_METHOD'] === 'POST') { 
    $id = $_POST['id'];
    $edit = $_POST['edit'];
    $first_name = $_POST['first_name'];
    $last_name = $_POST['last_name'];
    $email = $_POST['email'];
    $result=mysql_query("UPDATE user SET first_name='$first_name',last_name='$last_name',email='$email' WHERE id='$id'");
}

Also check your security, use mysql_real_escape_string

also you can make your checks bigger, check if submit button is pressed etc...