PHP/PDO : No result if a column = 0? - php

Question

I have a very simple function to check in the DB if we know an Artist (based on a unique ID) and if it's the case, I want to collect his infos :
function isArtistKnown($id_artist){
global $pdo;
$isKnownQuery = $pdo->query("SELECT * FROM artistes WHERE IDArtiste = '$id_artist'");
if($isKnownQuery->rowCount() > 0){
$KnownArtiste = $isKnownQuery->fetch(PDO::FETCH_OBJ);
return $KnownArtiste;
}else{
return $isKnownQuery->errorInfo();
}
}
The problem is following :
If the IDArtiste is known and another colmun called "last_tweet' (INT50) equals 0 then the PDO finds 1 result and $KnownArtiste is filled.
Now, If the IDArtiste is known but the colum "last_tweet" != 0 then the PDO doens't find any result (and errorInfo() equals 0000, which means : no error).
Do you have an idea where the problem comes from ?

Answer 1

The documentation states :
PDO::query() executes an SQL statement in a single function call,
returning the result set (if any) returned by the statement as a
PDOStatement object.
Which means, if there's no match, it returns no rows!

Answer 2

Quoting directly from the PHP PDOStatement::rowCount page:
PDOStatement::rowCount() returns the number of rows affected by the
last DELETE, INSERT, or UPDATE statement executed by the corresponding
PDOStatement object.
If the last SQL statement executed by the associated PDOStatement was
a SELECT statement, some databases may return the number of rows
returned by that statement. However, this behaviour is not guaranteed
for all databases and should not be relied on for portable
applications.
You can't use rowCount with SELECTs. Use this instead:
function isArtistKnown($id_artist){
global $pdo;
//If you don't use prepared statements, a kitten and a puppy die somewhere
$isKnownQuery = $pdo->prepare("SELECT * FROM artistes WHERE IDArtiste = :ida");
$isKnownQuery->bindValue(':ida', $id_artist);
$isKnownQuery->execute();
$KnownArtiste = $isKnownQuery->fetch(PDO::FETCH_OBJ);
if(isset($KnownArtiste->IDArtiste)){
return $KnownArtiste;
}else{
//Actually, in this case there's no error, just no artist
//so i'd use
return null;
//instead of
//return $isKnownQuery->errorInfo();
}
}

Answer 3

If you're going to return errorInfo() it'll always contain data whether there is an error or not. You should be returning a friendly user message to state that there are no rows found (the artist is not known to you)
function isArtistKnown($id_artist){
global $pdo;
$isKnownQuery = $pdo->query("SELECT * FROM artistes WHERE IDArtiste = '$id_artist'");
if ($isKnownQuery->rowCount() === 0){
return false;
}
$KnownArtiste = $isKnownQuery->fetch(PDO::FETCH_OBJ);
return $KnownArtiste
}
and validate:
$Validate = isArtistKnown(0);
if ($Validate === false){
echo "Artist is Not Known";
}else{
//Work with your data
}