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<?php $sunday = new DateTimeImmutable('Sunday'); $monday = new DateTimeImmutable('Monday'); foreach (new DatePeriod($sunday, new DateInterval('P1D'), 6) as $date) { $dow = $date->format('w'); $weekday = $sunday->add(new DateInterval('P' . $dow . 'D')); $dowISO = $date->format('N'); $weekdayISOM = $monday->add(new DateInterval('P' . ($dowISO - 1) . 'D')); $weekdayISOS = $sunday->add(new DateInterval('P' . $dowISO . 'D')); printf("STD: %s = %s\nISOM: %s = %s\nISOS: %s = %s\n\n", $dow, $weekday->format('l'), $dowISO, $weekdayISOM->format('l'), $dowISO, $weekdayISOS->format('l')); }
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
STD: 0 = Sunday ISOM: 7 = Sunday ISOS: 7 = Sunday STD: 1 = Monday ISOM: 1 = Monday ISOS: 1 = Monday STD: 2 = Tuesday ISOM: 2 = Tuesday ISOS: 2 = Tuesday STD: 3 = Wednesday ISOM: 3 = Wednesday ISOS: 3 = Wednesday STD: 4 = Thursday ISOM: 4 = Thursday ISOS: 4 = Thursday STD: 5 = Friday ISOM: 5 = Friday ISOS: 5 = Friday STD: 6 = Saturday ISOM: 6 = Saturday ISOS: 6 = Saturday

preferences:
159.1 ms | 403 KiB | 152 Q