CodingForums.com - Warning: fwrite() expects parameter 3 to be long, string

hi gang - I'm getting the following error when handling my form:
Warning: fwrite() expects parameter 3 to be long, string...on line 31

what I'm trying to do is submit my form values into a csv file and I was hoping that I could add column names - I create csv's with the majority of the code below all the time but I've never tried to add column names before so I don't know if maybe I'm not supposed to have 3 parameters in fwrite, or if $columns should be formed differently...or something else altogether?

as you can see, I echo out the $date and $frequency and those values display just fine, as do the $_POST values

PHP Code:


		
			
<?php

function protect($string) {

  $string = trim($string);

  return $string;

} 



if (isset($_POST['form_submit']) && ($_POST['submitForm'] == 1)) {

    $errors = array();

        foreach ($_POST['frequency'] as $key=> $value) {

            $freq = "$value, ";

        }

        $freq = substr($freq,0,-2);

    $date = date('n/j/Y');

    echo '<pre>';

    echo 'Frequency: '.$freq.'<br />';

    echo 'Date: '.$date.'<br />';

    echo '</pre>';

    $columns = 'Date, Pharmacy Store #, Agent Name, Address, Store Mgr Cooperative, Not Cooperative, Senior Traffic, Approaches, Frequency, Kiosk, Problems';

    $q1 = protect($_POST['pharmacy_id']);

    $q2 = protect($_POST['agent_name']);

    $q3 = protect($_POST['agent_address'].', '.$_POST['agent_city'].', '.$_POST['agent_state'].', '.$_POST['agent_zip']);

    $q4 = protect($_POST['store_cooperative']);

    $q5 = protect($_POST['senior_traffic']);

    $q6 = protect($_POST['approaches']);

    $q7 = protect($freq);

    $q8 = protect($_POST['kiosk']);

    $q9 = protect($_POST['problems']);

    $filename = 'data/data.csv';

    $csvData = "\"".$date."\",\"".$q1."\",\"".$q2."\",\"".$q3."\",\"".$q4."\",\"".$q5."\",\"".$q6."\",\"".$q7."\",\"".$q8."\",\"".$q9."\"\n";

    $handle = fopen($filename,"a");

    if ($handle) {

        fwrite($handle,$columns,$csvData);

        fclose($handle);

        //header("Location: ".WEBSITE_URL."/thank-you.php");

    }

    else {

        $errors['filenotupdated'] = 'There was an error writing to the file';

    }

  }

?>

the $errors['filenotupdated'] does not trip, but I'm not sure if that's because I have my $_POST and other variables echoing

any help is greatly appreciated!