How to check if card pin have been used? - php

Question

I am building a student result portal and I want each pin to one student for 5 times.
Here is my code:
if (!$error) {
$res=mysql_query("SELECT * from pin WHERE userid='$reg'");
$row=mysql_fetch_array($res);
$count = mysql_num_rows($res); // if regno correct it returns must be 1 row
if( $count == 1 && $row['userid']==$reg ) {
$pinid = $row['id'] ;
$check_hw = $row['hw'] ;
if ($check_hw <=4 ) {
$res=mysql_query("UPDATE pin SET userid='$reg',status='1',hw=hw+1 WHERE pin='$pin'");
$_SESSION['user'] = $row['userid'];
header("Location: access.php");
} else {
$errMSG = "Card Limit Exceeded";
}
} else {
$errMSG = "Card Used By Another user Or Limit Exceeded";
}
}
this what i want to do please help
if(user enter pin){
select status from pins where pin = pin
if(status = "used" or pin is tied to a different ID other that the student ID entered){
echo " card used and buy new scratch card "
header('Location: buypin.php');
}
else{
header('Location: rightplace.php');
set the status of this pin to "used" and tie that very pin to the students ID
}
}
i did rewrite the code to
if (!$error) {
$res=mysql_query("SELECT id,userid,hw FROM pin WHERE userid=" . (int)$reg);
$row=mysql_fetch_array($res);
$count = mysql_num_rows($res); // if regno correct it returns must be 1 row
if ($row = mysql_fetch_array($res)) {
$pinid = $row['id'] ;
$check_hw = $row['hw'] ;
if ($check_hw <=4 ) {
$res=mysql_query("UPDATE pin SET userid='$reg',status='1',hw=hw+1 WHERE pin='$pin'");
$_SESSION['user'] = $row['userid'];
header("Location: access.php");
}
else {
$errMSG = "Card Limit Exceeded";
}
} else {
$errMSG = "Card Used By Another user ";
}
}
my working code
if( isset($_POST['btn-signup']) ){
$reg = trim($_POST['reg']);
$reg = strip_tags($reg);
$reg = htmlspecialchars($reg);
$pin = trim($_POST['pin']);
$pin = strip_tags($pin);
$pin = htmlspecialchars($pin);
$res=mysqli_query($con,"SELECT * FROM pin WHERE pin ='$pin'");
$row=mysqli_fetch_array($res);
$check_id = $row['userid'];
// checking if the colum userid is empty
if ('' !== $row['userid']){
// if userid colum is not empty,reg no is correct and limit more than 4
if ($row['userid']==$reg && $row['hw']<=4) {
$errMSG = "log";
}else {
$errMSG = " Card Used Or Limit Exceeded";
}
}else{
$errMSG = "log";
}
}
?>
Thanks alot