Question

我想知道上周第一天的日期：

$date = new DateTime(NULL, new DateTimeZone('Pacific/Wake')); 
$date = $date->modify('previous week');
$date = $date->format('Y-m-d');

和

$date = new DateTime(NULL, new DateTimeZone('Pacific/Wake')); 
$date = $date->modify('last week');
$date = $date->format('Y-m-d');

两者都有效。但是有什么不同吗？

Answer 1

它们是相同的，如果你愿意，可以自己确认一下，PHP源代码可以在github上找到。

https://github.com/php/php-src/blob/master/ext/date/php_date.c#L1443

PHP_FUNCTION(strtotime)
{
    ...
    t = timelib_strtotime(initial_ts, strlen(initial_ts), NULL, DATE_TIMEZONEDB, php_date_parse_tzfile_wrapper); /* we ignore the error here, as this should never fail */

所以它调用timelib_strtotime，哪里可以找到它？幸运的是，这也是在线

https://github.com/php/php-src/blob/master/ext/date/lib/parse_date.c#L24743

timelib_time* timelib_strtotime(char *s, int len, struct timelib_error_container **errors, const timelib_tzdb *tzdb, timelib_tz_get_wrapper tz_get_wrapper)
{
    ...
    do {
        t = scan(&in, tz_get_wrapper);
#ifdef DEBUG_PARSER
            printf("%d\n", t);
#endif
    } while(t != EOI);
    ...

依赖于scan：

https://github.com/php/php-src/blob/master/ext/date/lib/parse_date.c#L835

static int scan(Scanner *s, timelib_tz_get_wrapper tz_get_wrapper)
{
     ...
     while(*ptr) {
         i = timelib_get_relative_text((char **) &ptr, &behavior);

调用timelib_get_relative_text

https://github.com/php/php-src/blob/master/ext/date/lib/parse_date.c#L561

static timelib_sll timelib_get_relative_text(char **ptr, int *behavior)
{
    while (**ptr == ' ' || **ptr == '\t' || **ptr == '-' || **ptr == '/') {
        ++*ptr;
    }
    return timelib_lookup_relative_text(ptr, behavior);
}

调用timelib_lookup_relative_text：

https://github.com/php/php-src/blob/master/ext/date/lib/parse_date.c#L536

static timelib_sll timelib_lookup_relative_text(char **ptr, int *behavior)
{
    ...
    for (tp = timelib_reltext_lookup; tp->name; tp++) {
        if (strcasecmp(word, tp->name) == 0) {
            value = tp->value;
            *behavior = tp->type;
        }
    }
    ...
}

反过来又使用在文件顶部定义的名为timelib_reltext_lookup的结构集：

https://github.com/php/php-src/blob/master/ext/date/lib/parse_date.c#L248

  static timelib_lookup_table const timelib_reltext_lookup[] = {
     { "first",    0,  1 },
     { "next",     0,  1 },
     { "second",   0,  2 },
     { "third",    0,  3 },
     { "fourth",   0,  4 },
     { "fifth",    0,  5 },
     { "sixth",    0,  6 },
     { "seventh",  0,  7 },
     { "eight",    0,  8 },
     { "eighth",   0,  8 },
     { "ninth",    0,  9 },
     { "tenth",    0, 10 },
     { "eleventh", 0, 11 },
     { "twelfth",  0, 12 },
     { "last",     0, -1 },
     { "previous", 0, -1 },
     { "this",     1,  0 },
     { NULL,       1,  0 }
  };

希望这足以证明它们在各方面都是相同的。

Answer 2

单词＆＃34; previous＆＃34;从PHP5开始支持，＆＃34; last＆＃34;从PHP4开始。两者的结果是相同的，两者仍然有效。

PHP DateTime：＆＃39;上周＆＃39;或者＆＃39;上周＆＃39;？

2 个答案: