PHP function to generate Google Calendar 'add event' links

gistfile1.php

//this function returns a URL that when clicked, attempts to  add a gcal event
function gcal_evt_href($data)
{
  //return a gcal href link for anchors

    //encode the data in the array for url formatting
    foreach($data as &$xx)
    {
        $xx = urlencode($xx);
    }
    $href = 'https://www.google.com/calendar/render?action=TEMPLATE&text='
            .$data['event_name'].'&dates='
            .$data['datetime_start'].'/'
            .$data['datetime_end'].'&details='
            .$data['description'].'&location='
            .$data['location_text'].'&trp=false&sprop='
            .$data['sprop_website'].'&sprop=name:'
            .$data['sprop_name'].'&pli=1&sf=true&output=xml';
    return $href;
} //end gcal_event_button

//example data to feed to the function
$data = array(
    'event_name'      => 'event_name',
    'datetime_start'  => '20130221', //YYYYMMDD
    'datetime_end'    => '20130222', //YYYYMMDD
    'location_text'   => 'name and address is fine',
    'description'     => 'longer desc for the details',
    'sprop_website'   => 'http://organization.com',
    'sprop_name'      => 'organization name'

);