Checks if a field is not empty.
boolean Core_Valid::not_empty( )
boolean public static function not_empty($value)
{
    if (is_object($value) && $value instanceof ArrayObject)
    {
        // Get the array from the ArrayObject
        $value = $value->getArrayCopy();
    }
    // Value cannot be NULL, false, '', or an empty array
    return !in_array($value, array(null, false, '', array()), true);
}