/**
* This function returns a boolean indicating if a date is
* valid by it's format.
*
* @param $date (Optional) A YDDate object, timestamp, array or string.
* @param $format (Optional) The format name. Default: 'ISO'.
* @param $family (Optional) If true, checks in all the format family. Default: true.
* @param $empty (Optional) If false, empty dates are not valid. Default: true.
*
* @returns True if the date is valid, false otherwise.
*
* @static
*/
function isValid($date, $format = 'ISO', $family = true, $empty = true)
{
if (!YDDate::parse($date, $format, $family, false)) {
return false;
}
if (!$empty && $date === YDDateFormat::getEmpty($format)) {
return false;
}
return true;
}
