php--常用的时间处理函数

天地四方曰宇，往古来今曰宙

时间是世界的重要组成部分，不论花开花落，还是云卷云舒都有它的影子。

但它源起何处？又将去向何方？没人知道答案，也不需要答案，我们需要的只是一个相对的起点来标识时间，现今世界普遍采用公元纪年法来表示。

公元纪年法以耶稣诞生日记为公元1年（没有公元0年），中国处于汉平帝刘衎（不会读。。。）登基第二年即元始元年。

关于时间的另一个概念是unix时间戳，是从1970年1月1日开始所经过的秒数，不考虑闰秒，什么是闰秒参考这里。

下面就来说说php中时间的处理方法，以获取当前时间为例

 <?php
     date_default_timezone_set('Asia/Shanghai');
     echo "now is ".date("Y-m-d H:i:s",time())."\n";
     echo "now is ".date("Y-m-d H:i:s",strtotime("now"))."\n";
     $date = new DateTime();
     echo "now is ".$date->format("Y-m-d H:i:s")."\n";
 ?>

时区设置

date_default_timezone_set用于设置时区，优先级别高于php.ini中设置的date.timezone属性，可设置的时区列表见这里，与之对应的是date_default_timezone_get获取由set函数设置的时区。

 <?php
     date_default_timezone_set('Asia/Shanghai');
     $date_set = date_default_timezone_get();
     //如果与配置文件中的时区设置相同则设置为美国时区
     if($date_set == ini_get("date.timezone")){
         date_default_timezone_set('America/Los_Angeles');
     }
     echo date("Y-m-d H:i:s")."\n";
 ?>

获取UNIX时间戳

常用的方法有三种：time(),microtime(),strotime("now")

 <?php
     error_reporting(E_ALL ^E_STRICT);
     echo "time is ".time()."\n";
     echo "strotime is ".strtotime("now")."\n";
     echo "mktime is ".mktime()."\n";
     echo "microtime is ".microtime()."\n";
     //参数设置为true返回浮点数表示的时间戳
     echo "in float microtime is ".microtime(true)."\n";
 ?>

mktime

mktime函数的参数全是关键字参数，关键字参数大家懂的可以从右到左省略，格式为时，分，秒，月，日，年

 <?php

     //年默认2014
     echo "mktime(10,10,10,10,12) is ".date("Y-m-d H:i:s",mktime(10,10,10,10,12))."\n";

     //这种写法会将2014当作月数，年还是默认的2014年
     echo "mktime(10,10,10,10,2014) is ".date("Y-m-d H:i:s",mktime(10,10,10,10,2014))."\n";

     echo "mktime(10,10,10,10,32,2014) is ".date("Y-m-d H:i:s",mktime(10,10,10,10,32,2014))."\n";
 ?>

出现了一些很奇妙的事情，2014年2014月变成了2020年4月，2014年10月32号变成了11月1号，看，mktime自动计算了相差部分。乍看之下感觉很神奇，细想下来又在情理之中，毕竟日期的相互转换是通过unix时间戳进行的，我们可以通过mktime的实现源码管中窥豹一下。

该函数源码位于ext/date/php_date.c 在1500行实现，篇幅所限只贴部分代码，兴趣的朋友可以下下来自己看，地址在这里.

 PHPAPI void php_mktime(INTERNAL_FUNCTION_PARAMETERS, int gmt)
 {
     zend_long hou = 0, min = 0, sec = 0, mon = 0, day = 0, yea = 0, dst = -1;
     timelib_time *now;
     timelib_tzinfo *tzi = NULL;
     zend_long ts, adjust_seconds = 0;
     int error;

     if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "|lllllll", &hou, &min, &sec, &mon, &day, &yea, &dst) == FAILURE) {
         RETURN_FALSE;
     }
     /* Initialize structure with current time */
     now = timelib_time_ctor();
     if (gmt) {
         timelib_unixtime2gmt(now, (timelib_sll) time(NULL));
     } else {
         tzi = get_timezone_info(TSRMLS_C);
         now->tz_info = tzi;
         now->zone_type = TIMELIB_ZONETYPE_ID;
         timelib_unixtime2local(now, (timelib_sll) time(NULL));
     }
     /* Fill in the new data */
     switch (ZEND_NUM_ARGS()) {
         case 7:
             /* break intentionally missing */
         case 6:
             if (yea >= 0 && yea < 70) {
                 yea += 2000;
             } else if (yea >= 70 && yea <= 100) {
                 yea += 1900;
             }
             now->y = yea;
             /* break intentionally missing again */
         case 5:
             now->d = day;
             /* break missing intentionally here too */
         case 4:
             now->m = mon;
             /* and here */
         case 3:
             now->s = sec;
             /* yup, this break isn't here on purpose too */
         case 2:
             now->i = min;
             /* last intentionally missing break */
         case 1:
             now->h = hou;
             break;
         default:
             php_error_docref(NULL TSRMLS_CC, E_STRICT, "You should be using the time() function instead");
     }
     /* Update the timestamp */
     if (gmt) {
         timelib_update_ts(now, NULL);
     } else {
         timelib_update_ts(now, tzi);
     }
     /* Support for the deprecated is_dst parameter */
     if (dst != -1) {
         php_error_docref(NULL TSRMLS_CC, E_DEPRECATED, "The is_dst parameter is deprecated");
         if (gmt) {
             /* GMT never uses DST */
             if (dst == 1) {
                 adjust_seconds = -3600;
             }
         } else {
             /* Figure out is_dst for current TS */
             timelib_time_offset *tmp_offset;
             tmp_offset = timelib_get_time_zone_info(now->sse, tzi);
             if (dst == 1 && tmp_offset->is_dst == 0) {
                 adjust_seconds = -3600;
             }
             if (dst == 0 && tmp_offset->is_dst == 1) {
                 adjust_seconds = +3600;
             }
             timelib_time_offset_dtor(tmp_offset);
         }
     }
     /* Clean up and return */
     ts = timelib_date_to_int(now, &error);
     ts += adjust_seconds;
     timelib_time_dtor(now);

     if (error) {
         RETURN_FALSE;
     } else {
         RETURN_LONG(ts);
     }
 }

阅读这段代码需知道一个重要的结构体timelib_time，在ext/date/lib/timelib_structs.h中声明

typedef struct timelib_time {
    timelib_sll      y, m, d;     /* Year, Month, Day */
    timelib_sll      h, i, s;     /* Hour, mInute, Second */
    double           f;           /* Fraction */
    int              z;           /* GMT offset in minutes */
    char            *tz_abbr;     /* Timezone abbreviation (display only) */
    timelib_tzinfo  *tz_info;     /* Timezone structure */
    signed int       dst;         /* Flag if we were parsing a DST zone */
    timelib_rel_time relative;

    timelib_sll      sse;         /* Seconds since epoch */

    unsigned int   have_time, have_date, have_zone, have_relative, have_weeknr_day;

    unsigned int   sse_uptodate; /* !0 if the sse member is up to date with the date/time members */
    unsigned int   tim_uptodate; /* !0 if the date/time members are up to date with the sse member */
    unsigned int   is_localtime; /*  1 if the current struct represents localtime, 0 if it is in GMT */
    unsigned int   zone_type;    /*  1 time offset,
                                  *  3 TimeZone identifier,
                                  *  2 TimeZone abbreviation */
} timelib_time;

现在来看看mktime,56行的timelib_update_ts函数位于ext/date/lib/tm2unixtime.c文件中，其作用是根据now中的日期信息计算相应的秒数并存入now->sse，来看看

 void timelib_update_ts(timelib_time* time, timelib_tzinfo* tzi)
 {
     timelib_sll res = ;

     do_adjust_special_early(time);
     do_adjust_relative(time);
     do_adjust_special(time);
     res += do_years(time->y);
     res += do_months(time->m, time->y);
     res += do_days(time->d);
     res += do_time(time->h, time->i, time->s);
     time->sse = res;

     res += do_adjust_timezone(time, tzi);
     time->sse = res;

     time->sse_uptodate = ;
     time->have_relative = time->relative.have_weekday_relative = time->relative.have_special_relative = ;
 }

8-11行计算相应时间类型的秒数，到这里已可了解mktime自动增减日期的原理，让我们看看do_days是如何实现的。day-1应该不难理解，mktime前面需要传入小时分钟等参数，在处理具体的某一天时默认为当天的0点0分0秒，所以要比实际的天数少一天。do_months,do_years等机制都相同，不再细述。

static timelib_sll do_days(timelib_ull day)
{
    return ((day - ) * SECS_PER_DAY);
}

当日期处理完成，我们回到php_date.c，在80行处通过timelib_date_to_int函数将now->sse返回，该函数位于ext/date/lib/timelib.c，具体的代码就不贴了。

strtotime

聊完了mktime，再来看看strtotime，同样先来几个例子

<?php

    echo "strtotime('+1 day',strtotime('2014/10/19')) is ".date("Y-m-d",strtotime("+1 day",strtotime("2014/10/19")))."\n";
    echo "strtotime('-30 day') is ".date("Y-m-d",strtotime("-30 day"))."\n";
    echo "strtotime('+1 week') is ".date("Y-m-d",strtotime("+1 week"))."\n";
    echo "strtotime('last Monday) is ".date("Y-m-d",strtotime("last Monday"))."\n";
?>

strtotime相较mktime要复杂很多，在于其对英文文本的解析过程，这里用到了词法解析工具re2c，原始文件位于ext/date/lib/parse_date.re,同目录下还有个parse_date.c是编译后的文件,parse_date.c太大，我们分析parse_date.re就可以了，以strtotime("+1 day")为例，下面是php_date.c中的实现代码

 PHP_FUNCTION(strtotime)
 {
     char *times, *initial_ts;
     size_t   time_len;
     int error1, error2;
     struct timelib_error_container *error;
     zend_long preset_ts = , ts;

     timelib_time *t, *now;
     timelib_tzinfo *tzi;

     tzi = get_timezone_info(TSRMLS_C);

     if (zend_parse_parameters_ex(ZEND_PARSE_PARAMS_QUIET, ZEND_NUM_ARGS() TSRMLS_CC, "sl", &times, &time_len, &preset_ts) != FAILURE) {
         /* We have an initial timestamp */
         now = timelib_time_ctor();

         initial_ts = emalloc();
         snprintf(initial_ts, , "@" ZEND_LONG_FMT " UTC", preset_ts);
         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 */
         timelib_update_ts(t, tzi);
         now->tz_info = tzi;
         now->zone_type = TIMELIB_ZONETYPE_ID;
         timelib_unixtime2local(now, t->sse);
         timelib_time_dtor(t);
         efree(initial_ts);
     } else if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|l", &times, &time_len, &preset_ts) != FAILURE) {
         /* We have no initial timestamp */
         now = timelib_time_ctor();
         now->tz_info = tzi;
         now->zone_type = TIMELIB_ZONETYPE_ID;
         timelib_unixtime2local(now, (timelib_sll) time(NULL));
     } else {
         RETURN_FALSE;
     }

     if (!time_len) {
         timelib_time_dtor(now);
         RETURN_FALSE;
     }

     t = timelib_strtotime(times, time_len, &error, DATE_TIMEZONEDB, php_date_parse_tzfile_wrapper);
     error1 = error->error_count;
     timelib_error_container_dtor(error);
     timelib_fill_holes(t, now, TIMELIB_NO_CLONE);
     timelib_update_ts(t, tzi);
     ts = timelib_date_to_int(t, &error2);

     timelib_time_dtor(now);
     timelib_time_dtor(t);

     if (error1 || error2) {
         RETURN_FALSE;
     } else {
         RETURN_LONG(ts);
     }
 }

if用来解析参数，分为有第二个参数和没有第二个参数的情况，这里略过不提，主要关注timelib_strtotime函数，它在parse_date.re中定义，返回解析后的timelib_time结构体。而timelib_strtotime又会调用parse_date.re中的scan方法来解析字符串，这里有几个重要的正则表达式

reltextnumber = 'first'|'second'|'third'|'fourth'|'fifth'|'sixth'|'seventh'|'eight'|'eighth'|'ninth'|'tenth'|'eleventh'|'twelfth';
reltexttext = 'next'|'last'|'previous'|'this';
reltextunit = (('sec'|'second'|'min'|'minute'|'hour'|'day'|'fortnight'|'forthnight'|'month'|'year') 's'?) | 'weeks' | daytext;

relnumber = ([+-]*[ \t]*[-]+);
relative = relnumber space? (reltextunit | 'week' );
relativetext = (reltextnumber|reltexttext) space reltextunit;
relativetextweek = reltexttext space 'week';

"+1 day"会被解析为relative,并进行relative的相关操作

    relative
    {
        timelib_ull i;
        DEBUG_OUTPUT("relative");
        TIMELIB_INIT;
        TIMELIB_HAVE_RELATIVE();

        while(*ptr) {
            i = timelib_get_unsigned_nr((char **) &ptr, );
            timelib_eat_spaces((char **) &ptr);
            timelib_set_relative((char **) &ptr, i, , s);
        }
        TIMELIB_DEINIT;
        return TIMELIB_RELATIVE;
    }

timelib_get_unsigned_nr 用来判断是"+"还是"-"，参数24用来指定最大的字符串长度，然后调用timelib_get_nr获取后面的具体数字，最后调用timelib_set_relative设置timelib_time 结构体中relative.d=1。

static timelib_ull timelib_get_unsigned_nr(char **ptr, int max_length)
{
    timelib_ull dir = ;

    while (((**ptr < '') || (**ptr > '')) && (**ptr != '+') && (**ptr != '-')) {
        if (**ptr == '\0') {
            return TIMELIB_UNSET;
        }
        ++*ptr;
    }

    while (**ptr == '+' || **ptr == '-')
    {
        if (**ptr == '-') {
            dir *= -;
        }
        ++*ptr;
    }
    return dir * timelib_get_nr(ptr, max_length);
}　

 static void timelib_set_relative(char **ptr, timelib_sll amount, int behavior, Scanner *s)
 {
     const timelib_relunit* relunit;

     if (!(relunit = timelib_lookup_relunit(ptr))) {
         return;
     }

     switch (relunit->unit) {
         case TIMELIB_SECOND: s->time->relative.s += amount * relunit->multiplier; break;
         case TIMELIB_MINUTE: s->time->relative.i += amount * relunit->multiplier; break;
         case TIMELIB_HOUR:   s->time->relative.h += amount * relunit->multiplier; break;
         case TIMELIB_DAY:    s->time->relative.d += amount * relunit->multiplier; break;
         case TIMELIB_MONTH:  s->time->relative.m += amount * relunit->multiplier; break;
         case TIMELIB_YEAR:   s->time->relative.y += amount * relunit->multiplier; break;

         case TIMELIB_WEEKDAY:
             TIMELIB_HAVE_WEEKDAY_RELATIVE();
             TIMELIB_UNHAVE_TIME();
             s->time->relative.d += (amount >  ? amount -  : amount) * ;
             s->time->relative.weekday = relunit->multiplier;
             s->time->relative.weekday_behavior = behavior;
             break;

         case TIMELIB_SPECIAL:
             TIMELIB_HAVE_SPECIAL_RELATIVE();
             TIMELIB_UNHAVE_TIME();
             s->time->relative.special.type = relunit->multiplier;
             s->time->relative.special.amount = amount;
     }
 }

timelib_set_relative

随后就和mktime一样调用相关处理函数转换为时间戳，有一点需要注意，timelib_set_relative的实现方式是直接在日期或月份上操作，下面这样的代码会出现问题

echo date("Y-m-d",strtotime("-1 month",strtotime("2014/03/31")))."\n";

输出结果为2014-03-03，按照上述流程，2014/03/31会转为2014/02/31处理，等价于mktime(00,00,00,2,31,2014),mktime的处理方式上文已经说过了:P

写一些常用的方法

知道了原理，用起来就很方便了。下面是使用频率较高的时间处理方法，例如获取前几周，前几天，取得本周第一天和最后一天的时间等等，不定期更新,github地址。

 <?php

     /**
     * process date
     * @author huntstack
     * @time 2014-10-18
     */
     class Process_Date{

         private $date;
         private $M,$D,$Y;

         /**
         * set the date for next operator
         * @parameter date:time string or timestamp
         */
         function __construct($date=""){
             if($date == "" || empty($date)){
                 $this->date = strtotime("now");
             }else if(gettype($date) == "string"){
                 $this->date = strtotime($date);
             }else if(gettype($date) == "integer"){
                 $this->date = $date;
             }else{
                 throw new Exception("paramter must be timestamp or date string or empty for current time");
             }
             $this->set_varibales();
         }

         public function set_date($date){
             $this->date = strtotime($date);
             $this->set_varibales();
         }

         private function set_varibales(){
             $this->M = date("m",$this->date);
             $this->D = date("d",$this->date);
             $this->Y = date("Y",$this->date);
         }

         /**
         * get the specified weeks
         * @parameter $i:numbers of week
         * @parameter $flag:0->last,1->next
         */
         public function get_week($i=0,$flag=1){
             if($flag == 0) return date("YW",strtotime("-$i week",$this->date));
             else if($flag == 1) return date("YW",strtotime("+$i week",$this->date));
         }

         /**
         * get the specified months
         * @parameter $i:numbers of month
         * @parameter $flag:0->last,1->next
         */
         public function get_month($i=0,$flag=1){
             if($flag == 0) return date("Y-m",mktime(0,0,0, $this->M-$i, 1, $this->Y));
             else if($flag == 1) return date("Y-m",mktime(0,0,0, $this->M+$i, 1, $this->Y));
         }

         /**
         * get the specified days
         * @parameter $i:numbers of day
         * @parameter $flag:0->last,1->next
         */
         public function get_day($i=0,$flag=1){
             if($flag == 0) return date("Y-m-d",mktime(0,0,0, $this->M, $this->D-$i, $this->Y));
             else if($flag == 1) return date("Y-m-d",mktime(0,0,0, $this->M, $this->D+$i, $this->Y));
         }

         /**
         * get the last $count days
         * @parameter count:number
         */
         public function get_last_days($count){
             $return  = array();
             for($i=1;$i<=$count;$i++){
                 array_push($return, $this->get_day($i,0));
             }
             return $return;
         }

         /**
         * get the next $count days
         * @parameter count:number
         */
         public function get_next_days($count){
             $return  = array();
             for($i=1;$i<=$count;$i++){
                 array_push($return, $this->get_day($i,1));
             }
             return $return;
         }

         /**
         * get the last $count weeks
         * @parameter count:number
         */
         public function get_last_weeks($count){
             $return  = array();
             for($i=1;$i<=$count;$i++){
                 array_push($return, $this->get_week($i,0));
             }
             return $return;
         }

         /**
         * get the next $count weeks
         * @parameter count:number
         */
         public function get_next_weeks($count){
             $return  = array();
             for($i=1;$i<=$count;$i++){
                 array_push($return, $this->get_week($i,1));
             }
             return $return;
         }

         /**
         * get the last $count months
         * @parameter count:number
         */
         public function get_last_month($count){
             $return  = array();
             for($i=1;$i<=$count;$i++){
                 array_push($return, $this->get_month($i,0));
             }
             return $return;
         }

         /**
         * get the next $count months
         * @parameter count:number
         */
         public function get_next_month($count){
             $return  = array();
             for($i=1;$i<=$count;$i++){
                 array_push($return, $this->get_month($i,1));
             }
             return $return;
         }

         /**
         * get the first day and the last day of a week
         */
         public function get_week_begin_end(){
             $return["begin"] = mktime(0,0,0, $this->M, $this->D-date("w",$this->date)+1, $this->Y);
             $return["end"] = mktime(23,59,59, $this->M, $this->D-date("w",$this->date)+7, $this->Y);
             return $return;
         }

         /**
         * get the first day and the last day of a month
         */
         public function get_month_begin_end(){
             $return["begin"] = strtotime("first day of",$this->date);
             $return["end"] = strtotime("last day of",$this->date);
             return $return;
         }
     }
 ?>

参考资料：

1.http://php.net/manual/zh/book.datetime.php

2.http://www.phppan.com/2011/06/php-strtotime/