PDO/SQL check for duplicates before inserting

Question

Rephrasing my question since it keeps getting marked as duplicate & pointing me to a question that I don't understand... can someone instead tell me which part of this is sql_api & needs to be changed??

I am trying to check my database for duplicate values before inserting new ones. I found a couple questions here asking that but couldn't find any examples where they are using PDO to connect to the database. Here is my insert statement that works fine:

if (isset($_POST['newName'])) {
$newName = trim($_POST['newName']);

if(!empty($newName)) {
    $addedQuery = $db->prepare("

    INSERT INTO type (typeName)
    VALUES (:newName)
    ");

    $addedQuery->execute([
        'newName' => $newName
    ]);
  }
}

This was the closest that I've gotten but it doesn't seem to work. I do have a unique requirement on the table that won't allow the duplicate values to actually be inserted but I am trying to alert the user to it. Any help is appreciated!!

if (isset($_POST['newName'])) {
$newName = trim($_POST['newName']);

$dupesql = "SELECT * FROM type WHERE typeName = :newName";
$duperaw = mysql_query($dupesql);

if($duperaw > 0) {
    echo (":newName already exists")
} else {
    if(!empty($newName)) {
    $addedQuery = $db->prepare("

    INSERT INTO type (typeName)
    VALUES (:newName)
    ");

    $addedQuery->execute([
        'newName' => $newName
    ]);
   }
  }
}