PHP - Will This Code Check If Value Is Null

I am using PDO to run query's and get data. How do I check if the PDO query returned a null value. I tried empty but that doesn't work because PDO array will always contain an SQL query. I want to check if the return value of that query is NULL . Help please.

I'm trying to get a nickname system working for a little project, but I've run into a problem.

This code that I wrote here gets the users nickname from their username:

Code: (php) [Select]
$user = $_GET['user'];
@mysql_select_db("db") or die( "Unable to select database");

$query = mysql_query("SELECT `nickname` FROM `info` WHERE `username`='$user'");

       WHILE($rows = mysql_fetch_array($query)):
           $nickname = $rows['nickname'];
           echo $nickname;
        endwhile;
?>

But the problem is, if the user doesn't have a nickname then it just turns up blank. How can I check if the output of $nickname is blank and if it is then just return their normal name ($user)

Thanks

Oh, and how to you format php code to look like php code on these forums?

i am trying to check if the array element (which would be a file) is null or not.  when i run it, uploading one file, it says "Please select some files to upload first!" X 3.  what am i doing wrong?

my code: http://pastebin.com/m0k3fEd2

Hi, I need to insert some code into my current form code which will check to see if a username exist and if so will display an echo message. If it does not exist will post the form (assuming everything else is filled in correctly). I have tried some code in a few places but it doesn't work correctly as I get the username message exist no matter what. I think I am inserting the code into the wrong area, so need assistance as to how to incorporate the username check code.

$sql="select * from Profile where username = '$username';
$result = mysql_query( $sql, $conn )
      or die( "ERR: SQL 1" );
if(mysql_num_rows($result)!=0)
{
process form
}
else
{
echo "That username already exist!";
}


the current code of the form


<?PHP
//session_start();
require_once "formvalidator.php";
$show_form=true;

if (!isset($_POST['Submit'])) {



$human_number1 = rand(1, 12);



$human_number2 = rand(1, 38);



$human_answer = $human_number1 + $human_number2;



$_SESSION['check_answer'] = $human_answer;
}

if(isset($_POST['Submit']))
{





if (!isset($_SESSION['check_answer'])) {
echo "<p>Error: Answer session not set</p>";
}


if($_POST['math'] != $_SESSION['check_answer']) {
echo "<p>You did not pass the human check.</p>";
exit();
}


   $validator = new FormValidator();
    $validator->addValidation("FirstName","req","Please fill in FirstName");







$validator->addValidation("LastName","req","Please fill in LastName");
$validator->addValidation("UserName","req","Please fill in UserName");
$validator->addValidation("Password","req","Please fill in a Password");
$validator->addValidation("Password2","req","Please re-enter your password");
$validator->addValidation("Password2","eqelmnt=Password","Your passwords do not match!");
$validator->addValidation("email","email","The input for Email should be a valid email value");
$validator->addValidation("email","req","Please fill in Email");
$validator->addValidation("Zip","req","Please fill in your Zip Code");
$validator->addValidation("Security","req","Please fill in your Security Question");
$validator->addValidation("Security2","req","Please fill in your Security Answer");
    if($validator->ValidateForm())
    {
        $con = mysql_connect("localhost","uname","pw") or die('Could not connect: ' . mysql_error());
        mysql_select_db("beatthis_beatthis") or die(mysql_error());
$FirstName=mysql_real_escape_string($_POST['FirstName']); //This value has to be the same as in the HTML form file
$LastName=mysql_real_escape_string($_POST['LastName']); //This value has to be the same as in the HTML form file
$UserName=mysql_real_escape_string($_POST['UserName']); //This value has to be the same as in the HTML form file
$Password= md5($_POST['Password']); //This value has to be the same as in the HTML form file
$Password2= md5($_POST['Password2']); //This value has to be the same as in the HTML form file
$email=mysql_real_escape_string($_POST['email']); //This value has to be the same as in the HTML form file
$Zip=mysql_real_escape_string($_POST['Zip']); //This value has to be the same as in the HTML form file
$Birthday=mysql_real_escape_string($_POST['Birthday']); //This value has to be the same as in the HTML form file
$Security=mysql_real_escape_string($_POST['Security']); //This value has to be the same as in the HTML form file
$Security2=mysql_real_escape_string($_POST['Security2']); //This value has to be the same as in the HTML form file



$sql="INSERT INTO Profile (`FirstName`,`LastName`,`Username`,`Password`,`Password2`,`email`,`Zip`,`Birthday`,`Security`,`Security2`) VALUES ('$FirstName','$LastName','$UserName','$Password','$Password2','$email','$Zip','$Birthday','$Security','$Security2')"; 
//echo $sql;
if (!mysql_query($sql,$con)) {

 die('Error: ' . mysql_error());

} else{



mail('email@gmail.com','A profile has been submitted!',$FirstName.' has submitted their profile',$body);

echo "<h3>Your profile information has been submitted successfully.</h3>";
}

mysql_close($con);
        $show_form=false;
    }
    else
    {
        echo "<h3 class='ErrorTitle'>Validation Errors:</h3>";

        $error_hash = $validator->GetErrors();
        foreach($error_hash as $inpname => $inp_err)
        {
            echo "<p class='errors'>$inpname : $inp_err</p>\n";
        }        
    }
}

if(true == $show_form)
{
?>

I am trying to update the database with isset to set the value of the variable to either null or the value entered by the user. Currently, if no value has been entered null is being set as a string causing the date field to populate with zeros. How do I code it so that it populates or sets the value as null and not as string null?   Here's my code: (yes I know sql injections it's still in development  ) <?php