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<?php $week_number = 20; $year = 2012; $monday = strtotime($year."W".str_pad($week_number,2,0,STR_PAD_LEFT)."1"); $sunday = strtotime($year."W".str_pad($week_number,2,0,STR_PAD_LEFT)."7"); var_dump($year."W".str_pad($week_number,2,0,STR_PAD_LEFT)."1"); echo "From " . date("l", $monday) . " " . date("j", $monday) . " of " . date("F", $monday) . " of " . $year . " to " . date("l", $sunday) . " " . date("j", $sunday) . " of " . date("F", $sunday) . " of " . $year;
Output for 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 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 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 - 8.3.6
string(8) "2012W201" From Monday 14 of May of 2012 to Sunday 20 of May of 2012
Output for 5.0.0 - 5.0.5
string(8) "2012W201" From Monday 7 of May of 2012 to Sunday 13 of May of 2012
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9
string(8) "2012W201" From Thursday 1 of January of 2012 to Thursday 1 of January of 2012

preferences:
311.36 ms | 402 KiB | 460 Q