how i can make a php page that adds values and if the value already exists to deletes it instead?

[giannis196]

how i can make a php page that adds values to the database, and if the value already exist to delete it instead of add it?
I am trying to do it but i am making a mistake and it only "deletes values".

```
<?php
require("database.php");
    if(empty($username) || empty($password)){
        echo "error";
    }else{
        $cdtitle=$_POST["cds"];
        $cdartist=$_POST["kal"];
        $query= 'SELECT FROM cds WHERE cdtitle=:cdtitle && cdartist=:cdartist';
        $result = $sql->prepare($query);
        $result->execute([":cdtitle" => $cdtitle, ":cdartist" => $cdartist]);
        $a = $result->fetchAll();

    if($a>0){
        $cdtitle=$_POST["cds"];
        $cdartist=$_POST["kal"];
        $query= 'DELETE FROM cds WHERE cdtitle=:cdtitle && cdartist=:cdartist';
        $result = $sql->prepare($query);
        $result->execute([":cdtitle" => $cdtitle, ":cdartist" => $cdartist]);
        $a = $result->fetchAll();
    echo "Deleted!";
    }else{
        $add = "INSERT INTO cds(username, cdtitle, cdartist) VALUES (:username, :cdtitle, :cdartist)";
        $result = $sql->prepare($add);
        $result->execute([":username" => $username ,":cdtitle" => $cdtitle, ":cdartist" => $cdartist]);
        $result->fetchAll();
        echo "Added!";
    }
}
?>
```

ok where is my mistake? how i can make it this way that it will add the value to the database if it doesn't exists and it will delete the value from the database if it exist?

[niche]

Query your table to initialize values then do your nested if statement.