Checking for empty result (php, pdo, mysql)

You're throwing away a result row when you do $sth->fetchColumn(). That's not how you check if there's any results. you do

if ($sth->rowCount() > 0) {
  ... got results ...
} else {
   echo 'nothing';
}

relevant docs here: http://php.net/manual/en/pdostatement.rowcount.php

If you have the option of using fetchAll() then if there are no rows returned it will just be and empty array.

count($sql->fetchAll(PDO::FETCH_ASSOC))

will return the number of rows returned.

Even though this is an old thread, I thought I would weigh in as I had to deal with this lately.

You should not use rowCount for SELECT statements as it is not portable. I use the isset function to test if a select statement worked:

$today = date('Y-m-d', strtotime('now'));

$sth = $db->prepare("SELECT id_email FROM db WHERE hardcopy = '1' AND hardcopy_date <= :today AND hardcopy_sent = '0' ORDER BY id_email ASC");

//I would usually put this all in a try/catch block, but kept it the same for continuity
if(!$sth->execute(array(':today'=>$today))) 
{
    $db = null ;
    exit();
}

$result = $sth->fetch(PDO::FETCH_OBJ)

if(!isset($result->id_email))
{
    echo "empty";
}
else
{
    echo "not empty, value is $result->id_email";
}

$db = null;

Of course this is only for a single result, as you might have when looping over a dataset.