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<?php $test = strtotime("2014-01-01"); // тут может преобразование отличаться echo "week: ".date("W", $test);
Output for 4.4.1 - 4.4.9, 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.7
week: 01
Output for 4.3.0 - 4.3.11, 4.4.0, 5.0.0 - 5.0.4
week: 1
preferences:
250.54 ms | 402 KiB | 352 Q