Delete the record if its exist , else insert - php

Question

I have a click favorite star , i want to check in data base if the record is exist it will delete the record , if it not exist it will insert the record ,what is the problem the record not inserted
<?php
include "config.php";
header('Content-Type: application/json');
$landmarkid = $_GET['landmarkid'];
$userid = $_GET['userid'];
try {
$query = mysqli_query($con,"SELECT * from favourite WHERE userid =$userid AND L_ID = $landmarkid");
if(mysqli_num_rows($query) > 0)
{
$q1 = mysqli_query($con,"DELETE from favourite WHERE userid =$userid AND L_ID = $landmarkid");
if($q1){
echo '{"Deleted":"true"}';
}
else {
echo '{"Deleted":"false"}';
}
}
else {
$q2 = mysqli_query($con,"INSERT INTO favourite (userid,L_ID) VALUES ( $userid, $landmarkid) ");
if($q2){
echo '{"inserted":"true"}';
}
else {
echo '{"inserted":"false"}';
}
}
} catch (Exception $e) {
echo 'Caught exception: ', $e->getMessage(), "\n";
}
?>

Answer 1

Try to add single quotation marks to your insert statement and see if it works. Change this statement;
$q2 = mysqli_query($con,"INSERT INTO favourite (userid,L_ID) VALUES ( $userid, $landmarkid) ");
To this;
$q2 = mysqli_query($con,"INSERT INTO favourite (userid,L_ID) VALUES ( '$userid', '$landmarkid') ");
Let me know if it helps or if you find a problem.

Answer 2

I have rewritten your code below.
Some points:
Your code was vulerable to SQL injection so assuming id is a numeric value I forced the input vars ($userid and $landmarkid) to be integers using (int) casting.
Your first checking query can return a COUNT value, it's better than returning a * and then you can check a specific value for your if statements, $result['numb'].
I have properly escaped your php variables in the SQL, but you really should be trying to use Prepared Statements for this.
I dont think you need the try{} catch {} here as your current code will never throw exceptions (as far as I'm aware)
Add a LIMIT to your delete statements so you can never delete more than an intended number of row. This acts as a failsafe so you don't inadvertantly manage to delete the whole table.
<?php
include "config.php";
header('Content-Type: application/json');
$landmarkid = (int)$_GET['landmarkid'];
$userid = (int)$_GET['userid'];
try {
$query = mysqli_query($con,"SELECT COUNT(*) as numb FROM
favourite WHERE userid = ".$userid." AND
L_ID = ".$landmarkid);
$result = mysqli_fetch_aray($query);
if($result['numb'] > 0)
{
$q1 = mysqli_query($con,"DELETE FROM favourite
WHERE userid = ".$userid." AND L_ID = ".$landmarkid."
LIMIT 1");
print "deleted";
}
else {
$q2 = mysqli_query($con,"INSERT INTO favourite (userid,L_ID)
VALUES ( ".$userid", ".$landmarkid.") ");
print "inserted";
}
}
catch (Exception $e) {
echo 'Caught exception: ', $e->getMessage(), "\n";
}
?>