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<?php header('Content-type: text/plain'); foreach(array(1,2) as $n) { var_dump(date("c",strtotime("first day of +$n months"))); }
Output for 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 - 7.1.10, 7.2.0 - 7.2.33, 7.3.12 - 7.3.31, 7.4.0 - 7.4.25, 7.4.27 - 7.4.33, 8.0.0 - 8.0.12, 8.0.14 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
string(25) "2012-11-01T08:56:34+01:00" string(25) "2012-12-01T08:56:34+01:00"
Output for 7.3.32 - 7.3.33, 7.4.26, 8.0.13
string(25) "2012-11-01T07:56:34+00:00" string(25) "2012-12-01T07:56:34+00:00"
Output for 5.1.0 - 5.1.6, 5.2.0 - 5.2.17
string(25) "1970-01-01T01:00:00+01:00" string(25) "1970-01-01T01:00:00+01:00"
Output for 5.0.0 - 5.0.5
string(25) "1970-01-01T00:59:59+01:00" string(25) "1970-01-01T00:59:59+01:00"
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9
string(1) "c" string(1) "c"

preferences:
256.85 ms | 402 KiB | 356 Q