Database update fails to work within php - php

Question

I have a fairly simple php page which displays a list of results from the database in a table, and the end of the row is a Dismiss button, I want to click this and have the database update to reset the flag which is original query thus dismissing the message.
I have looked at loads of examples here and have built a form around the button to call a separate php file which should execute the query to change the database and return to the original page which will be redrawn with one record less.
Everything works as expected but the database update doesn't occur.
Table drawing:
<table>
<!-- lay out the table and populate the header row -->
<tr>
<th>Site</th>
<th>Name</th>
<th>Alarm</th>
<th>Error</th>
<th>Confirm</th>
</tr>
<?php
$sql = "SELECT * FROM `hive_data` WHERE ack = 'y' "; //SQL query to find entries where the ack field is set 'y'
$result = $conn->query($sql);
while($row = mysqli_fetch_array($result)) { //start while loop to draw table one line per returned row
$line = $row["row_id"]; //define page variables from table columns
$site = $row["site"];
$module = $row["module_id"];
$alarm = $row["alarm"];
$error = $row["error"];
?>
<tr>
<!-- display each row returned listing the fields lists and a box to dismiss the alert -->
<td><?php echo $site; ?></td>
<td><?php echo $module; ?></td>
<td><?php echo $alarm; ?></td>
<td><?php echo $error; ?></td>
<td>
<form action = "data/dismiss_alerts.php" method="post">
<!-- last column of the table is a dismiss button -->
<input type="hidden" value="<?php echo $line ?>" name="line"> <!-- hidden input to send the row number to be changed -->
<input type="submit" value="Dismiss"> <!-- submit button to post data to dismiss_alerts.php -->
</form>
</td>
</tr>
<?php
} //close the while statement
?>
</table>
Dismiss alert page:
if(isset($_POST['line'])) {
$rowToUpdate = intval($_POST['line']);
$sql = "UPDATE `hive_data` SET `ack` = 'n' WHERE row_id = " . $rowToUpdate . "";
$result = mysqli_query($conn, $sql);
header('Location: ../index.php?page=home'); // return to sending page..
}
The execution refreshes the original page but the database is not updated.
Troubleshooting dismiss alert page:
if(isset($_POST['line'])) {
$rowToUpdate = intval($_POST['line']);
$sql = "UPDATE `hive_data` SET `ack` = 'n' WHERE row_id = " . $rowToUpdate . "";
echo $sql;
if($conn->connect_error) {
echo "Connection failed";
} else {
echo "Connected";
if($conn->query($sql) === TRUE) {
echo "Record updated successfully";
} else {
echo "Error updating record: " . $conn->error;
}
}
}
The first if clause works fine so I stay on the dismiss alerts page and get the echo of my query and a message saying the database is connected but the second if clause never reports anything.
UPDATE `hive_data` SET `ack` = 'n' WHERE row_id = 253Connected
I have tested the query inline on the calling page so that it actually deletes the last line of the table on every refresh so I am pretty sure that bit works, but I am really stumped with this.
Any ideas?

Answer 1

OK so after spending all morning on this ten minutes after posting here I found that despite my troubleshooting line above the db was not connected I had to build a connect and disconnect into the page and it works fine.
Now to read up on prepared statements and re-do it all that way :-)