/**
* Return the date as yyyymmdd for sorting
*
* @param string $date
* @param boolean getNumericKey if true, returns an 8-digit numeric key that incorporates the effect of bef/aft date modifiers
* @return string or int if getNumericKey is used
*/
public static function getDateKey($date, $getNumericKey = false)
{
$result = '';
$year = '';
$month = '';
$day = '';
$monthError = $dayError = false;
// don't set errors anymore
$fields = array();
// this should match 0-9+ or alphabetic(including accented)+
preg_match_all('/(\\d+|[^0-9\\s`~!@#%^&*()_+\\-={}|:\'<>?;,\\/"\\[\\]\\.\\\\]+)/', $date, $fields, PREG_SET_ORDER);
for ($i = 0; $i < count($fields); $i++) {
$field = $fields[$i][1];
$num = $field + 0;
// force conversion to number
if (StructuredData::isYear($num)) {
if (!$year) {
$year = $num;
}
// take the first year and ignore later numbers
} else {
if ($m = StructuredData::getAlphaMonth($field)) {
if (!$month) {
$month = $m;
}
// take the first month and ignore later (in case of date ranges)
} else {
if ($i > 0 && StructuredData::isYear($fields[$i - 1][1] + 0) && StructuredData::isNextYear($year, $field)) {
$year++;
// 1963/4 or 1963/64
} else {
if (StructuredData::isDay($num) && (!StructuredData::isNumMonth($num) || $i > 0 && StructuredData::getAlphaMonth($fields[$i - 1][1]) || $i < count($fields) - 1 && StructuredData::getAlphaMonth($fields[$i + 1][1]))) {
if (!$day) {
$day = $num;
}
// take the first day and ignore later
} else {
if (StructuredData::isNumMonth($num)) {
if (!$month) {
$month = $num;
}
// take the first month and ignore later
}
}
}
}
}
}
if ($year) {
$result = "{$year}";
// force conversion back to string
if ($month && !$monthError) {
$result .= $month < 10 ? "0{$month}" : $month;
if ($day && !$dayError) {
$result .= $day < 10 ? "0{$day}" : $day;
} else {
if ($getNumericKey) {
$result .= "01";
}
}
} else {
if ($getNumericKey) {
$result .= "0101";
}
}
if ($getNumericKey) {
$result = (int) $result;
if (preg_match("/\\b(bef|before)\\b/i", $date)) {
$result -= 10000;
// subtract a year
} else {
if (preg_match("/\\b(aft|after)\\b/i", $date)) {
$result += 10000;
// add a year
}
}
}
}
return $result;
}