PHP date_interval_create_from_date_string() 函数

<?php
// Each set of intervals is equal.
$i = new DateInterval('P1D');
pre_print($i);
$i = DateInterval::createFromDateString('1 day');
pre_print($i);

$i = new DateInterval('P2W');
pre_print($i);
$i = DateInterval::createFromDateString('2 weeks');
pre_print($i);

$i = new DateInterval('P3M');
pre_print($i);
$i = DateInterval::createFromDateString('3 months');
pre_print($i);

$i = new DateInterval('P4Y');
pre_print($i);
$i = DateInterval::createFromDateString('4 years');
pre_print($i);

$i = new DateInterval('P1Y1D');
pre_print($i);
$i = DateInterval::createFromDateString('1 year + 1 day');
pre_print($i);

$i = new DateInterval('P1DT12H');
pre_print($i);
$i = DateInterval::createFromDateString('1 day + 12 hours');
pre_print($i);

$i = new DateInterval('PT3600S');
pre_print($i);
$i = DateInterval::createFromDateString('3600 seconds');
pre_print($i);

function pre_print($params)
{
    echo '<pre>';
    print_r($params);
    echo '</pre>';
}
?>