SQL error when updating member table PDO php

Afternoon,

Currently I am writing a program that allows an admin to update the members datebase.

My code is as follows:

    $member_id = $formdata['update']; 
$surname = $formdata['surname'];
$other_name = $formdata['othername'];
$contactmethod = $formdata['contactmethod'];
$email = $formdata['email'];
$mobilenum = $formdata['mobilenum'];
$phonenum = $formdata['phonenum'];
$occupation = $formdata['occupation'];    
$userpass = $formdata['userpass'];
if(!isset($formdata['magazine']))
   $magazine = 0;
else
   $magazine = 1;

//Get ready to talk to the DB
$db = getDBConnection();
//Make a prepared query so that we can use data binding and avoid SQL injections. 
$insertUser = $db->prepare('INSERT into member VALUES
                          (:surname, :other_name, :contact_method,
                           :email, :mobile, :landline, :magazine, :street,
                           :suburb, :postcode, :password,
                           :occupation) WHERE member_id=$member_id');
//Bind the data from the form to the query variables.
//Doing it this way means PDO sanitises the input which prevents SQL injection.
$insertUser->bindParam(':surname', $surname, PDO::PARAM_STR);
$insertUser->bindParam(':other_name', $other_name, PDO::PARAM_STR);
$insertUser->bindParam(':contact_method', $contactmethod, PDO::PARAM_STR);
$insertUser->bindParam(':email', $email, PDO::PARAM_STR);
$insertUser->bindParam(':mobile', $mobilenum, PDO::PARAM_STR);
$insertUser->bindParam(':landline', $phonenum, PDO::PARAM_STR);
$insertUser->bindParam(':magazine', $magazine, PDO::PARAM_INT);
$insertUser->bindParam(':street', $streetaddr, PDO::PARAM_STR);
$insertUser->bindParam(':suburb', $suburbstate, PDO::PARAM_STR);
$insertUser->bindParam(':postcode', $postcode, PDO::PARAM_INT);
$insertUser->bindParam(':password', $userpass, PDO::PARAM_STR);
$insertUser->bindParam(':occupation', $occupation, PDO::PARAM_STR);

Current error is within WHERE member_id=$member_id

I have no idea what the error is and how to fix it.

Any tips?