Read CSV and compare code then populate fields (wedding)

// http://www.gravityhelp.com/forums/topic/wedding-rsvp-dynamic-population
// originally http://www.gravityhelp.com/forums/topic/database-look-up-validation
// validate a code entered in field 1 of your form with a text file
// change the 2 here to your form ID
add_filter('gform_validation_2', 'validate_code');
function validate_code($validation_result){
        // this assumes the code is entered in field one on your form
        // change this input_ number if it's a different field
        // is_code_valid function can be found below.  This calls the function and if FALSE is returned, a validation error is returned
        if(!is_code_valid($_POST['input_1'])){
        $validation_result['is_valid'] = false;
        foreach($validation_result['form']['fields'] as &$field){
            // field 1 is the field where we want to show the validation message
            if($field['id'] == 1){
                $field['failed_validation'] = true;
                                $field['validation_message'] = 'The code you entered is invalid: please try again.';
                break;
            }
        }
    }
    return $validation_result;
}

// use this function to validate the entered code
// called from the validate_code function above
function is_code_valid($thiscode){
        // read all the codes in from the guests.txt file
        // change the name and location of this file

        /* here is the format of the file
        12345,Chris Hajer,Abraham Lincoln
        56789,Phillipo Berrio,Ron Paul,George Washington
        222,Don King,Jesse Ventura,Jeb Bush,Barack Obama
        5566,The Situation
        */

        $codes = file('/home/content/html/website/guests.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
        // read each line and split the line into the $codes array, on commas
        foreach($codes as $code){
                $guests = explode (",", $code);
                // compare the entered code to all codes in the file until we find a match
                // the [0] indexed item is our code
                if($thiscode == $guests[0]){
                        // the entered code matched, so grab all the names AND return true
                        // the populate_guest_names function can be found below
                        populate_guest_names($guests);
                        // return true because this is a valid code
                        return TRUE;
                }
        }
        // if we did not have a match and are out of codes, return FALSE
        return FALSE;
}

// populate all the guest names that are associated with this password
// this function accepts an array which is the code and all the names associated with it
// called from the is_code_valid function above
function populate_guest_names($names){

        // count the number of guests associated with this code
        // subtract 1 so we don't count the password as an array item
        $number_of_names = count($names)-1;

        // the functions below can be simplified and don't account for any number of guests less than 1 or more than 4
        if ($number_of_names == 1) {
                // split the $names[1] array item on the space between first and last name
                $guest1 = explode (" ",$names[1]);
                // assign the first and last name to the $_POST to populate hidden inputs in the form
                $_POST['input_2'] = $guest1[0];
                $_POST['input_3'] = $guest1[1];

        } elseif ($number_of_names == 2) {
                // repeat the same process for 2, 3 or 4 names, just assigning more variables
                $guest1 = explode (" ",$names[1]);
                $_POST['input_2'] = $guest1[0];
                $_POST['input_3'] = $guest1[1];

                $guest2 = explode (" ",$names[2]);
                $_POST['input_4'] = $guest2[0];
                $_POST['input_5'] = $guest2[1];

        } elseif ($number_of_names == 3) {

                $guest1 = explode (" ",$names[1]);
                $_POST['input_2'] = $guest1[0];
                $_POST['input_3'] = $guest1[1];

                $guest2 = explode (" ",$names[2]);
                $_POST['input_4'] = $guest2[0];
                $_POST['input_5'] = $guest2[1];

                $guest3 = explode (" ",$names[3]);
                $_POST['input_6'] = $guest3[0];
                $_POST['input_7'] = $guest3[1];

        } else {

        $guest1 = explode (" ",$names[1]);
        $_POST['input_2'] = $guest1[0];
        $_POST['input_3'] = $guest1[1];

        $guest2 = explode (" ",$names[2]);
        $_POST['input_4'] = $guest2[0];
        $_POST['input_5'] = $guest2[1];

        $guest3 = explode (" ",$names[3]);
        $_POST['input_6'] = $guest3[0];
        $_POST['input_7'] = $guest3[1];

        $guest4 = explode (" ",$names[4]);
        $_POST['input_8'] = $guest4[0];
        $_POST['input_9'] = $guest4[1];

        }
}