Blank page when executing a database query?

Question

What's wrong with this code? I'm getting a blank page for this?

<?php
define( '_JEXEC', 1 );
define('JPATH_BASE', __DIR__);
require_once ( JPATH_BASE .'/includes/defines.php' );
require_once ( JPATH_BASE .'/includes/framework.php' );
$app = JFactory::getApplication('site');
$db = JFactory::getDbo();
$user = JFactory::getUser();
$profile = JUserHelper::getProfile($user->id);

if( $user->username == 'THE_USER_1' )
{
    $query = $db->getQuery(true);
    $query->select($db->quoteName('username'));
    ->from($db->quoteName('#table_name#'));
    ->where($db->quoteName('username') . ' = '. $db->quote($user->username));
    $db->setQuery($query);

    $result = $db->loadResult();

if($result) { 
   echo "<p> You have already filled the form.</p>";
}
else {
    // continue to form page
}
elseif( $user->username == 'THE_USER_2' )
{
    // some code 
}
else
{
    echo "<p> Sorry, you can't access this page.</p>";
}
?>

Answer 1

Firstly, you are missing a closing brackets in your if statement. Also, you are carrying on the database query having ended the previous line with a semi-colon. I don't know what you have also done when defining the database table, but you should replace #table_name# with #__table_name.

Copy and paste the code below which includes the missing closing bracket, removal of additional semi-colons and correct table name:

<?php
define( '_JEXEC', 1 );
define('JPATH_BASE', __DIR__);
require_once ( JPATH_BASE .'/includes/defines.php' );
require_once ( JPATH_BASE .'/includes/framework.php' );
$app = JFactory::getApplication('site');
$db = JFactory::getDbo();
$user = JFactory::getUser();
$profile = JUserHelper::getProfile($user->id);

if( $user->username == 'THE_USER_1' )
{
    $query = $db->getQuery(true);
    $query->select($db->quoteName('username'))
          ->from($db->quoteName('#__table_name'))
          ->where($db->quoteName('username') . ' = '. $db->quote($user->username));
    $db->setQuery($query);

    $result = $db->loadResult();

    if($result) { 
       echo "<p> You have already filled the form.</p>";
    }
}
elseif( $user->username == 'THE_USER_2' )
{
    // some code 
}
elseif( $user->username !== 'THE_USER_1' || $user->username !== 'THE_USER_2' )
{
    echo "<p> Sorry, you can't access this page.</p>";
}
else 
{
    echo "display form";
}
?>

Hope this helps