/**
* Returns a pages change frequency calculated by pages age and number of
* versions. Google expects always, hourly, daily, weekly, monthly, yearly
* or never as values.
*
* @see http://support.google.com/webmasters/bin/answer.py?hl=en&answer=183668&topic=8476&ctx=topic
*
* @return SS_Datetime
*/
public function getChangeFrequency()
{
if ($freq = GoogleSitemap::get_frequency_for_class($this->owner->class)) {
return $freq;
}
$date = date('Y-m-d H:i:s');
$created = new SS_Datetime();
$created->value = $this->owner->Created ? $this->owner->Created : $date;
$now = new SS_Datetime();
$now->value = $date;
$versions = $this->owner->Version ? $this->owner->Version : 1;
$timediff = $now->format('U') - $created->format('U');
// Check how many revisions have been made over the lifetime of the
// Page for a rough estimate of it's changing frequency.
$period = $timediff / ($versions + 1);
if ($period > 60 * 60 * 24 * 365) {
$freq = 'yearly';
} elseif ($period > 60 * 60 * 24 * 30) {
$freq = 'monthly';
} elseif ($period > 60 * 60 * 24 * 7) {
$freq = 'weekly';
} elseif ($period > 60 * 60 * 24) {
$freq = 'daily';
} elseif ($period > 60 * 60) {
$freq = 'hourly';
} else {
$freq = 'always';
}
return $freq;
}
