Updating a form entry in php/mysql with checkboxes? - php

Question

How can I allow the user submitting a form, to update his entry on "re-submission"
for example
12345678910 (unique id) , submitted the form with selections,
12345678910 , re-submitted with new selections
what's the function responsible for "automatically" updating such kind of form entries.
I know that I can use a check if the entry exists, but how do I update it if it exists and insert it in a new row if it doesn't ...
function checkstudentid($studentid)
{
$con = connectvar();
mysql_select_db("database1", $con);
$result = mysql_query(
"SELECT * FROM table WHERE studentid='$studentid' LIMIT 1");
if(mysql_fetch_array($result) !== false)
....
// I want to add the entry here since it doesn't exist...with checkboxes
// else , I want to update if it already exists
}
Now I'm also not completely positive if the above code will work...but this is what I have for starters, if there is any other way or if the method I'm using is "wrong" , I would appreciate the heads up...or if what I'm trying to is even possible (the way I'm doing it)...
NOTES
I only have one php file which the form submits to.
I am not using a login/registration system
I do not want to display all the data in a table using HTML, just an
"automatic" update if the studentid already exists in the table

Answer 1

If I were using a deprecated method to interact with a database, I would probably just do this:
<?php
function checkstudentid($studentid) {
$con = connectvar();
mysql_select_db("database1", $con);
$result = mysql_query(
"SELECT * FROM table WHERE studentid='$studentid' LIMIT 1");
$query = '';
if (mysql_num_rows($result) > 0) {
$query = "UPDATE table SET column1='$value_one', column2='$value_two' WHERE studentid='$studentid'";
} else {
$query = "INSERT INTO table VALUES('$new_id', '$value_one', '$value_two')";
}
if (mysql_query($query)) {
return true;
} else {
return false;
}
}
?>
But then again, I would use PDO to interact with the DB.
Here is a simple PDO example (you just have to write the function to return the connection):
<?php
function checkstudentid($studentid) {
$update = false;
$dbh = formPDOConnection();
$query = "SELECT studentid FROM table WHERE studentid=:id";
$stmt = $dbh->prepare($query);
$stmt->bindValue(':id', $studentid, PDO::PARAM_STR);
if ($stmt->execute()) {
if ($stmt->rowCount()) {
$update = true;
}
} else {
return 'failure to execute query';
}
// if we just need to update
if ($update) {
$update = "UPDATE table SET value1=:v1,
value2=:v2 WHERE studentid=:id";
$stmt = $dbh->prepare($update);
$stmt->bindValue(':id', $studentid, PDO::PARAM_STR);
$stmt->bindValue(':v1', $value_one, PDO::PARAM_STR);
$stmt->bindValue(':v2', $value_two, PDO::PARAM_STR);
} else {
$insert = "INSERT INTO table VALUES(:id,:v1,v2)";
$stmt = $dbh->prepare($insert);
$stmt->bindValue(':id', $new_id, PDO::PARAM_STR);
$stmt->bindValue(':v1', $value_one, PDO::PARAM_STR);
$stmt->bindValue(':v2', $value_two, PDO::PARAM_STR);
}
return $stmt->execute();
}
?>
Save yourself a headache and stop using mysql_*

Answer 2

You can use INSERT... ON DUPLICATE KEY UPDATE... on your mysql code instead use the logic in your PHP.
Here's a sample:
INSERT INTO `category` (`id`, `name`) VALUES (12, 'color')
ON DUPLICATE KEY UPDATE `name` = 'color';
Reference: http://dev.mysql.com/doc/refman/5.6/en/insert-on-duplicate.html