- var_dump: documentation ( source)
- mktime: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
var_dump( mktime(0,0,0,date("m")-6,date("d"),date("Y")) );
var_dump( date("m")-6 );
var_dump($x = "現在 " . date("Y-m-d H:i:s"));
var_dump($x = "現在 " . strtotime(""));
var_dump($x = "6ヶ月前 " . date("Y-m-d H:i:s",strtotime("-6 month")));
var_dump($x = "6ヶ月前 " . strtotime("-6 month"));