Updating multiple rows from PDO fetch query - php

Question

I understand to call and update since rows using prepared statements but I'm having trouble understanding how to update multiple records.
I have a simple attendance register with a select box to define if they attended or not. I call the rows in a table format:
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<table>
<tbody>
<tr>
<th scope="col">Name</th>
<th scope="col">Attendance</th>
</tr>
<?php if($Event_list->rowCount() > 0) {
foreach ($Event_list->fetchAll() as $Event_list_row) { ?>
<tr>
<td>
<?php echo ucwords($Event_list_row['firstname'])." ".ucwords($Event_list_row['surname']); ?>
</td>
<td>
<input type="hidden" name="id" value="<?php echo $Event_list_row['booking_id']; ?>">
<select name="outcome">
<option value="0">Choose</option>
<option value="1">Yes</option>
<option value="2">No</option>
</select>
</td>
</tr>
<?php } } ?>
</tbody>
</table>
<input type="submit" value="Update" name="update">
</form>
I thought I could just use foreach again to update each record, but clearly I'm doing something wrong:
if(isset($_POST["update"])) {
$Update_ID = $_POST["id"];
$Update_Outcome = $_POST["outcome"];
foreach($_POST['id'] as $count => $id) {
$Attendance_Update_SQL = "
UPDATE event_booking SET
`confirmed`= :outcome
WHERE `id`= :id";
$Attendance_Update = $dbconn->prepare($Attendance_Update_SQL);
$Attendance_Update->bindParam(':id', $Update_ID[$count], PDO::PARAM_STR);
$Attendance_Update->bindParam(':outcome', $Update_Outcome[$count], PDO::PARAM_STR);
if($Attendance_Update->execute()) {
// Add in success message?
}
}
}
I get the following error:
Warning: Invalid argument supplied for foreach()
relating to the foreach row

Answer 1

Quick Fix:
rename name="id" to name="id[]"
rename name="outcome" to name="outcome[]"
Note: this syntax and reliance on index is problematic when you add checkbox types to a form.
Ok, the biggest problem is your input names are going to conflict
eg <select name="outcome"> will only set the last records outcome from your form.
I would use var_dump($_POST) to understand your post data
Suggestion, rename your "name" attributes as name="record[id][property]"...
<select name="record[<?php echo $Event_list_row['booking_id']; ?>][outcome]">
<option value="0">Choose</option>
<option value="1">Yes</option>
<option value="2">No</option>
</select>
You would then use
foreach( $_POST['record'] as $id => $data )
where $id and $data['outcome'] is now clearer to understand and use.