Where to check for any results - php

Question

Ok so I have 2 classes. Photo class and PhotoMapper class.
Photo class contains all the values and outputs them.
PhotoMapper sets the values to the Photo class, by a assign class, like this:
$query = "SELECT * FROM users";
$query = $this->_pdo->prepare($query);
$query->bindValue(":id", $photo->id());
$query->execute();
$data = $query->fetch();
$photo->assign($data);
And the assign:
public function assign($data){
if (is_array($data)) {
foreach ($data as $name => $value)
{
$this->{'_' . $name} = $value;
}
}
}
Now where would i check for if $query->rowCount() > 0 ?
Should i inside is_array after the foreach, make a $this->rowCount = .. ?
What would be best to perform this check? I would like to check for the rowCount outside of both classes..
$photo = new Photo($albumID, $photoID, $view, $userID);
$photoMapper->select($photo, $view);
Is how it looks outside the classes. How can i check and output error if select(which is the query above) didnt find any rows?
I would need to have 2 queries? One to check, and one to select them? or?..

Answer 1

Well, if you're expecting data from the fetch operation but there isn't any (you could simply find out by checking if $data has any contents), you should throw an Exception. The following code snippet would typically be placed before the fetch:
// ...
$query->execute();
if ( !( $data = $query->fetch() ) ) {
throw new Exception('photo could not be loaded');
}
$photo->assign($data);
// ...
However, if you want the code to continue regardless, you can reverse the if condition, and put the assign call inside the statement;
$query->execute();
if ( ( $data = $query->fetch() ) ) {
$photo->assign($data);
}