Question

I am currently using a PHP framework which basically uses a wrapper for PDO, and am stumped on a problem. I have a page which takes any number of post variables, which could be any combination of the following:

":fullname" => $_POST['fullName'],
    ":universityID" => $_POST['university'], 
    ":gpa" => $_POST['gpa'], 
    ":major" => $_POST['major'], 
    ":gradYear" => $_POST['gradYear'], 
    ":photo" => "", 
    ":description" => $_POST['description'], 
    "howDidYouHear" => $_POST['howDidYouHear']

And I have an update statement which should look something like this:

$affectedRows = getDatabase()->execute('UPDATE user SET universityID = :universityID, 
gpa = :gpa, etc, WHERE fullName=:fullName', array(':universityID' =>     
$_POST['universityID'], ':gpa' => $_POST['gpa']));

Now the problem is if I do this sort of update statement I will be overwriting old data in the table, most of which is still valid. What I want to do is only update rows which I have new information for, and not touch the other ones. Is there a way to figure out within the query which ones should and should not be changed?

Answer 1

$sets = array();
$vals = array();

for ($_POST as $key => $value) {
  if ($value == '') { continue; }
  switch ($key) {
  case "university":
    $sets[] = 'universityID = ?';
    $vals[] = $value;
    break;
  case "gpa":
  case "major":
  case "gradYear":
  case "description":
  case "howDidYouHear":
    $sets = "$key = ?";
    $vals = $value;
    break;
  }

$sql = 'UPDATE user SET ' . implode(', ', $sets) . 'WHERE fullname = ?';
$vals[] = $_POST['fullname'];
$affectedRows = getDatabase()->execute($sql, $vals);