PHP/MySQL PDO/Update Rows

Question

I'm here trying to update my DB rows without deleting/creating new ones all the time. Currently, my DB creates new entries everytime I run this block of code. Instead of spamming my DB, I just want to change some of the values.

     <?php
try {
    $conn = new PDO("mysql:host=localhost;port=3306;dbname=dbname", Username, password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 }
catch(PDOException $e){
echo "Connection failed: " . $e->getMessage();
}

if(isset($_POST['mUsername']))
{
    $mUsername = urldecode($_POST['mUsername']);
    $mEvent = urldecode($_POST['mEvent']);
    $mChat = urldecode($_POST['mChat']);
    $mlongitude = urldecode($_POST['mlongitude']);
    $mlatitude = urldecode($_POST['mlatitude']);

    $sqlUPDATE = "UPDATE users 
                        SET lastEvent=:lastEvent, lastChat=:lastChat,
                            lastLong=:lastLong, lastLatt=:lastLatt 
                      WHERE name=:name";

$stmt = $conn->prepare($sqlUPDATE);
$stmt->bindParam(':lastEvent', $mEvent);
$stmt->bindParam(':lastChat', $mChat);
$stmt->bindParam(':lastLong', $mlongitude);
$stmt->bindParam(':lastLatt', $mlatitude);
$stmt->bindParam(':name', $mUsername);
$stmt->execute();
}
echo "successfully updated";
?>

My assumption is my final line, the $results area. I believe it's just treating this an a new entry instead of an update. How do I go about just replacing values? some values will not change, like the username, and sometimes longitude/latitude won't need to be changed. Would that have to be a separate query, should I split this in to two scripts? Or could I just enter a blank, null value? Or would that end up overwriting the ACTUAL last coordinates, leaving me with null values? Looking for any help or guides or tutorials. Thank you all in advance.

Answer 1

When using prepared statements, you should also make a habbit of following the set rules. Use named parameters. Try this:

if(isset($_POST['mUsername']))
{
    $mUsername = urldecode($_POST['mUsername']);
    $mEvent = urldecode($_POST['mEvent']);
    $mChat = urldecode($_POST['mChat']);
    $mlongitude = urldecode($_POST['mlongitude']);
    $mlatitude = urldecode($_POST['mlatitude']);

    $sqlUPDATE = "UPDATE users SET lastEvent= :lastEvent, lastChat= :lastChat, lastLong= :lastLong, lastLatt= :lastLatt WHERE name= :name";
    $q = $conn->prepare($sqlUPDATE);
    $results = $q->execute(array(':name'=>$mUsername, ':lastEvent'=>$mEvent, ':lastChat'=>$mChat, ':lastLong'=>$mlongitude, ':lastLatt'=>$mlatitude));
}

Answer 2

lots of syntax error in your code. It is simple to use bindParam

$sqlUPDATE = "UPDATE users 
                        SET lastEvent=:lastEvent, lastChat=:lastChat,
                            lastLong=:lastLong, lastLatt=:lastLatt 
                      WHERE name=:name";// you forget to close statement in your code

$stmt = $conn->prepare($sqlUPDATE);
$stmt->bindParam(':lastEvent', $mEvent);
$stmt->bindParam(':lastChat', $mChat);
$stmt->bindParam(':lastLong', $mlongitude);
$stmt->bindParam(':lastLatt', $mlatitude);
$stmt->bindParam(':name', $mUsername);
$stmt->execute();

read http://php.net/manual/en/pdostatement.bindparam.php