Converting to PDO prepared statements from mysqli - php

Question

I have the following bit of code, that selects a table, loops through all the values which match an actor and displays the reviews for that actor.
include("app/config/db.php");
$aid=$actor['id'];
$query = "SELECT * FROM `reviews` WHERE `actor_id` = $aid";
$result = $mysqli->query($query);
$num_results = $result->num_rows;
if( $num_results ){
//loop to show each records
while( $row = $result->fetch_assoc() ){
extract($row);
echo "<span class=\"review-score\">";
echo $row['score']*10;
echo "</span>";
echo " by <strong>";
echo $row['author'];
echo "</strong>";
echo " on <strong>";
echo $row['created_at'];
echo "</strong>";
echo "<p class=\"review-body\">";
echo $row['body'];
echo "</p>";
echo "</br>";
}
}else{
echo "No records found.";
}
$result->free();
$mysqli->close();
I want to convert to using PDO prepared statements.
This is what I've tried. It doesn't display any of the reviews assigned to the actor. Please help
include("app/config/db.php");
$aid=$actor['id'];
$st = DBase::singleton()
->prepare(
'select * ' .
'from `reviews` ' .
'where `actor_id` like :aid ' .
'limit 0,10');
$st->bindParam(':aid', $aid, PDO::PARAM_STR);
if ($st->execute())
{
while ($row = $st->fetch(PDO::FETCH_OBJ))
{
echo "<span class=\"review-score\">";
echo $st['score']*10;
echo "</span>";
echo " by <strong>";
echo $st['author'];
echo "</strong>";
echo " on <strong>";
echo $st['created_at'];
echo "</strong>";
echo "<p class=\"review-body\">";
echo $st['body'];
echo "</p>";
echo "</br>";
}
}
DBase:singleton
static public function singleton()
{
if (!is_object(self::$pdo))
{
self::$pdo = new PDO('mysql:dbname=' . self::DATABASE . ';host=' . self::HOST,
self::USERNAME,
self::PASSWORD);
}
return self::$pdo;
}

Answer 1

You're storing each row's result in $row, but not accessing $row when you want to display the data.
while ($row = $st->fetch(PDO::FETCH_OBJ))
{
...
echo $st['score']*10;
The echo line should be:
echo $row->score*10;
You're also fetching objects but accessing the data as an array.
thats how I was taught to write a while loop.. how else could I do it?
My point is that if assign a variable with successive values of the row, then the data is in that variable, not in the object that iterates over rows. What you've done is analogous to this:
for ($i = 0; $i < $count; $i++) {
echo $count;
}
Whereas in that example one should do this instead to get successive values in the loop:
for ($i = 0; $i < $count; $i++) {
echo $i;
}