PHP / MySQL. Could not update data: Query was empty - php

Question

First of all I like to say that I'm super bad at this type of stuff so my code can be totally useless.
The mission is to create a system that will ask the user to scan two ID's, userID and itemID. After the scan has been successful I want these values to be transported to a PHP document.
Here I'd like to run a MySQL query which will update the value of userID where itemID match the database.
So my problem is that I get this message after running my query:
userID:202 itemID:8204 Could not update data: Query was empty. And ofc my database remains empty.
I think the problem is that the query can't read the $_GET variables. But I have no clue so please help me, Thanks!
This is my form:
<form id="checkin" name="checkin" action="test.php">
<input type="button" onclick="checkIn()" value="Check in Item">
</form>
The function:
<script>
function checkIn(){
var userID=parseInt(prompt ("Scan userid"), 10);
var itemID=parseInt(prompt ("Scan itemid"), 10);
if(userID!=null && itemID!=null){
window.location.href= "http://localhost/webapp/test.php?userID=" + userID + "&itemID=" + itemID;
alert ("working so far userID:"+ userID + " --- itemID:" + itemID);
}
}
</script>
At last the PHP:
$con = mysql_connect("localhost", "root", "", "book1");
$db = mysql_select_db('book1');
if (isset($_GET["userID"]) && isset($_GET["itemID"])) {
$userID1 = (int)$_GET["userID"];
$itemID2 = (int)$_GET["itemID"];
$test = "userID: ".$_GET["userID"]." "."itemID: ".$_GET["itemID"];
echo $test;
}
if (!$con) {
die('Could not connect: '.mysql_error());
}
$upd = mysql_query('UPDATE INTO booking SET userID ="$userID" WHERE ID ="$itemID');
$retval = mysql_query($upd, $con);
if (!$retval) {
die('Could not update data: '.mysql_error());
}
echo "Updated data successfully\n";

Answer 1

Invalid arguments # mysql_connect()
$con=mysql_connect("localhost", "root", "") or die ('Connection failed' . mysql_error());
$db = mysql_select_db('book1',$con);
UPDATE INTO need to change to UPDATE ....
Also you have userID assigned to variable $userID1 and itemID assigned to $itemID2. But in your query it is wrong. Query is updated now.
Mysql Manual
Also missing quotes at WHERE ID ="$itemID'
$upd = mysql_query("UPDATE booking SET userID ='$userID1' WHERE ID ='$itemID2'", $con);
P.S. Usage of mysql_* functions is not advised, instead use mysqli_*

Answer 2

Your DB connection string might looks mysqli_. In mysql_, you don't want to specify the DB Name as parameter.
$con=mysql_connect("localhost", "root", "", "book1");
This should be,
$con=mysql_connect("localhost", "root", "");
You add unnecessary INTO in UPDATE query..
Refer the manual
Try this,
UPDATE booking SET ....
instead of,
UPDATE INTO booking SET ....
You might also want to read this: Why shouldn't I use mysql_* functions in PHP?

Answer 3

Correct your connection as per manual and also correct Update syntax
Check PHP CONNECTION Manual
$con=mysql_connect("localhost", "root", "") OR die('Could not connect');
$db = mysql_select_db('book1',$con);
if(isset($_GET["userID"]) && isset($_GET["itemID"])){
$userID1= (int) $_GET["userID"];
$itemID2= (int) $_GET["itemID"];
$test = "userID: ". $_GET["userID"] . " " . "itemID: ". $_GET["itemID"];
echo $test;
}
$upd = mysql_query("UPDATE booking SET userID='".$userID."' WHERE ID=$itemID");
$retval = mysql_query( $upd);
if(! $retval){
die('Could not update data: ' . mysql_error());
}
echo "Updated data successfully\n";
}

Answer 4

#user3751216 the error of the "syntax" problem it's generated on this line
$upd = mysql_query("UPDATE booking SET userID='".$userID."' WHERE ID=$itemID");
$retval = mysql_query( $upd);
If you put your code like this, it should resolve the problem of the SQL syntax
$upd = ("UPDATE booking SET userID='".$userID."' WHERE ID=$itemID");
$retval = mysql_query( $upd);
Let me now if you already resolve the problem.