MySQL UPDATE changes value to '0' instead of the provided integer when using bind_param

Question

Using AJAX I try to update table 'forminfo' in a MySQL database, calling the php script via GET and providing an id (integer value). However, when I call changeRequestedQ.php?id=4 for instance, the table cell will update to 0, not 4.

The column 'requestedQ' is formatted as INT(11). When I try to update $id = 4 manually, it works and the table cell is updated to 4.

require_once("msqli_config.php"); $id = $_GET['id']; // doesn't work, table cell updates to 0, whatever integer value I pass through file.php?id=<int> $id = (int)$_GET['id']; // no change in outcome $id = 4; // works, table cell updates to 4 try { $stmt1 = $mysqli->prepare("UPDATE forminfo SET requestedQ = ? WHERE id = 1;"); $stmt1->bind_param("i", $id); $stmt1->execute(); $stmt1->close(); } catch (Exception $e) { error_log($e); exit(); } $mysqli->close();

I have tried forcing PHP to parse the value as integer using (int)$_GET['id'], but there was no difference.

Additional variations (not using prepared statements):

$sql = "UPDATE forminfo SET requestedQ = '4' WHERE id = 1"; $mysqli->query($sql); // updates to 4 echo $sql; // UPDATE forminfo SET requestedQ = '4' WHERE id = 1 $sql = "UPDATE forminfo SET requestedQ = 4 WHERE id = 1"; $mysqli->query($sql); // updates to 4 echo $sql; // UPDATE forminfo SET requestedQ = 4 WHERE id = 1 $sql = "UPDATE forminfo SET requestedQ = '" . $id . "' WHERE id = 1"; $mysqli->query($sql); // updates to 0 echo $sql; // UPDATE forminfo SET requestedQ = '4' WHERE id = 1 $sql = "UPDATE forminfo SET requestedQ = " . $id . " WHERE id = 1"; $mysqli->query($sql); // updates to 0 echo $sql; // UPDATE forminfo SET requestedQ = 4 WHERE id = 1

UPDATE Being desperate, as I couldn't get my head around the difference in result between the previously mentioned pieces of code, I tried if this might be a specific browser issue. It turnes out that the above code works like a charm in MS Edge, and also in Google Chrome in Incognito mode, just not in a normal session. How can this be? Does it have to do with caching? I disabled cache in developers tools, but this didn't help...

Yes, it will return array(1) { ["id"]=> string(1) "4" } as expected — nucleaR
– nucleaR, Commented Jan 26, 2019 at 18:08
Can you try $stmt1 = $mysqli->prepare("UPDATE forminfo SET requestedQ = " . $id . " WHERE id = 1;"); //$stmt1->bind_param("i", $id); just to rule out the binding as the issue. — user3783243
– user3783243, Commented Jan 26, 2019 at 18:14
So it is definitely something with the $id variable. Is there code between the assignment, your var_dump, and the query execution? $id being reassigned to a string is the only thing I could see. — user3783243
– user3783243, Commented Jan 26, 2019 at 18:20

nucleaR · Accepted Answer · 2019-01-27 12:42:17Z

I've solved my problem. Thinking that this was a PHP/MySQL thing, I never looked into my browsers behaviour, nor the request and response parameters. My bad...

It turnes out that a browser plugin in Chrome was sending a second empty GET request (so without the query string) to the same destination, after the original request finished loading. Withoud $_GET['id'] defined, the table cell updates to 0. Removed the plugin, everything works.

In that case a good idea would be wrapping this whole thing in if(!empty($_GET['id'])) { then it will only execute when you have an id.
@user3783243 I added if (!isset($_GET['id'])) exit("No id provided");, which is good practice indeed.

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