update mysql as user updates textbox value - php

Question

i want to update value(s) as a student change value(s) in correction or update form.
till know i'm able to fetch and display values in text boxes on the bases of name selected from dropdown list from data base using ajax and json. but when i try to update database it do not works...
HTML:
<select name="u_stu" id="u_stu" onchange="show(this.value);" style="float:right; height:30px; width:180px;">
<option selected="selected" disabled="disabled">Choose</option>
<option>stu1</option>
<option>stu2</option>
<option>stu3</option>
</select>
name: <input type="text" id="name" name="name" style="float:right; height:20px; width:200px;"/><br /><br />
age: <input type="text" id="age" name="age" style="float:right; height:20px; width:200px;" /><br /><br />
phone: <input type="text" id="phone" name="u_ver_txt" style="float:right; height:20px; width:200px;" /><br /><br />
address: <input type="text" id="add" name="add" style="float:right; height:20px; width:200px;" /><br /><br />
hobby: <input type="text" id="hobby" name="hobby" style="float:right; height:20px; width:200px;" /><br /><br />
<input type="submit" value="Submit" name="u_s2" id="u_s2" style="position:relative; top:-180px; "/>
MYSQL PHP
<?php
$c=mysql_connect("localhost","abc","xyz");
mysql_select_db("root");
if(isset($_POST['u_s2']))
{
$name=$_POST["name"];
$age=$_POST["age"];
$phone=$_POST["phone"];
$address=$_POST["address"];
$hobby=$_POST["hoddy"];
$id=$_POST["u_id"];
$q2="UPDATE student SET
name=$name,age=$age,phone=$phone,address=$address,hobby=$hobby WHERE Sr. no=$id";
mysql_query($q2);
}
?>

Answer 1

You need something like this:
$q= "update student set name = '".$name."', age = '".$age."', phone = '".$phone."', address = '".$address."', hobby = '".$hobby."' WHERE user = 'the user id'";
You should use a WHERE statement as well like the above example so that you can be sure that you are updating the correct row.
You should also consider using mysql_real_escape_string function:
$name = mysql_real_escape_string($_POST['name']);
http://php.net/manual/en/function.mysql-real-escape-string.php
If this will be an updating form you should also include the value in the input fields and etc. so they will see the values and update what they need.
I also suggest that you use mysqli functions instead of mysql functions as mysql is no longer supported and deprecated.