evolution of Period string representation API

version3.php

<?php

use League\Period\Period;

$period = new Period('2021-01-01', '2021-04-01');
echo $period; //displays 2021-01-01T00:00:00.000000Z/2021-04-01T00:00:00.000000Z

version4-10.php

<?php

use League\Period\Period;

$period = new Period('2021-01-01', '2021-04-01', Period::EXCLUDE_ALL);
echo $period;                     // displays 2021-01-01T00:00:00.000000Z/2021-04-01T00:00:00.000000Z
echo $period->toIso8601();        // displays 2021-01-01T00:00:00.000000Z/2021-04-01T00:00:00.000000Z
echo $period->toIso8601('Y-m-d'); // displays 2021-01-01/2021-04-01
echo $period->format('Y-m-d');    // displays (2021-01-01, 2021-04-01)

version4-4.php

<?php

use League\Period\Period;

$period = new Period('2021-01-01', '2021-04-01', Period::EXCLUDE_ALL);
echo $period;                  // displays 2021-01-01T00:00:00.000000Z/2021-04-01T00:00:00.000000Z
echo $period->format('Y-m-d'); // displays (2021-01-01, 2021-04-01)

version5.php

<?php

use League\Period\Bounds;
use League\Period\Period;

$period = Period::fromDate('2021-01-01', '2021-04-01', Bounds::ExcludeAll);
echo $period->toIso8601();          // displays 2021-01-01T00:00:00.000000Z/2021-04-01T00:00:00.000000Z
echo $period->toIso8601('Y-m-d');   // displays 2021-01-01/2021-04-01
echo $period->toIso80000('Y-m-d');  // displays (2021-01-01, 2021-04-01)
echo $period->toBourbaki('Y-m-d');  // displays ]2021-01-01, 2021-04-01[

echo Period::fromIsoBourbaki('Y-m-d', ']2021-01-01, 2021-04-01[')->toIso80000('Y-m-d'); // displays (2021-01-01, 2021-04-01)
echo Period::fromIso80000('Y-m-d', '(2021-01-01, 2021-04-01)')->toBourbaki('Y-m-d');    // displays ]2021-01-01, 2021-04-01[
echo Period::fromIso8601('Y-m-d', '2021-01-01/2021-04-01', Bounds::ExcludeAll)->toIso8601('Y-m-d'); // displays 2021-01-01/2021-04-01