I am getting these errors:
Notice: Undefined index: first_name in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 13
Notice: Undefined index: last_name in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 14
Notice: Undefined index: age in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 15
Notice: Undefined index: mobile in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 16
Notice: Undefined index: email in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 17
Notice: Undefined index: address in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 18
Notice: Undefined index: club_role in /Applications/XAMPP/xamppfiles/htdocs/Assesment/add_student.php on line 19 Error: Duplicate entry '' for key 'PRIMARY'
Here is my code:`
    <h1> Add a new student</h1>
    <p>Add a new student to the system using the form below</p>
    <?php
    /*information posted from booking form*/
    $first_name=$_POST['first_name'];
    $last_name=$_POST['last_name'];
    $age=$_POST['age'];
    $mobile=$_POST['mobile'];
    $email=$_POST['email'];
    $address=$_POST['address'];
    $club_role=$_POST['club_role'];
    /*connect to DBMS*/
    $con=mysql_connect("localhost", "root", "");
    if (!$con)
    {
        die ('Could not connect: ' .mysql_error());
    }
    /*connect to Database*/
    mysql_select_db("91368_jurgen_glee",$con);
    /*insert into records*/
    $sql="INSERT INTO glee (`first_name`, `last_name`, `age`, `mobile`, `email`, `address`, `club_role`)
    VALUES ('$first_name', '$last_name', '$age', '$mobile', '$email', '$address', '$club_role')";
    mysql_Query($sql, $con) or die ('Error: '.mysql_error());
    $result=mysql_query("SELECT *
        WHERE `first_name` = '$first_name'
        AND `last_name` = '$last_name'
        AND `age` = '$age'
        AND `mobile` = '$mobile'
        AND `email` = '$email'
        AND `address` = '$address' 
        AND `club_role` = $club_role'");
        while ($row = mysql_fetch_array($reslut))
    /*close DBMS Connection*/
    mysql_close($con);
    ?>      
                <div id="body"> 
                    <h1> Add a new student</h1>
                    <p>Add a new student to the system using the form below</p>
                    <form name="add_student" action="add_student.php">
                        <table class="add_student">
                            <tr>
                                <td class="form">
                                    <b>First Name</b></br>
                                    <input type="text" name="first_name" size="30" value="">
                                </td>
                                <td class="form">
                                    <b>Last Name</b></br>
                                    <input type="text" name="last_name" size="30" value="">
                                </td>
                            </tr>   
                            <tr>
                                <td class="form">
                                    <b>Mobile</b></br> 
                                    <input type="text" size="10" name="mobile" min="1" max="10" value="">
                                </td>
                                <td class="form">
                                    <b>Email</b></br>
                                    <input type="text" name="email" size="15" value="">
                                </td>
                                <td class="form">
                                    <b>Age</b></br>
                                    <input type="number" name="age" size="2" min="1" max="30" value="">
                                </td>
                            </tr>
                                    <td class="form">
                                        <br>
                                    </h1><b>Address</b></h1>
                                    <select name="address">
                                        <option value="01">Please select one</option>
                                        <option value="02">Red Beach</option>
                                        <option value="03">Orewa</option>
                                        <option value="04">Silverdale</option>
                                        <option value="05">Dairy Flat</option>
                                    </select>
                                </td>
                                <br>
                                    <td class="form">
                                        <br>
                                    </h1><b>Club Role</b></h1>
                                    <select name="club-role">
                                        <option value="01">Please select one</option>
                                        <option value="02">Lead</option>
                                        <option value="03">Backstage</option>
                                        <option value="04">Chorus</option>
                                        <option value="05">Orchestra</option>
                                    </select>
                                </td>
                            </tr>
                            <tr>
                                <td colspan="2" class="submit">
                                    <br>
                                    <input type="submit" value="SUBMIT">
                                </td>
                            </tr>
                        </table>
                    </form>
            </div> 
            </div>
    </body> 
</html> 
`
 
     
     
    