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
1 <?php 2 date_default_timezone_set('Asia/Shanghai'); 3 echo "now is ".date("Y-m-d H:i:s",time())."\n"; 4 echo "now is ".date("Y-m-d H:i:s",strtotime("now"))."\n"; 5 $date = new DateTime(); 6 echo "now is ".$date->format("Y-m-d H:i:s")."\n"; 7 ?>
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。
1 <?php 2 date_default_timezone_set('Asia/Shanghai'); 3 $date_set = date_default_timezone_get(); 4 //如果与配置文件中的时区设置相同则设置为美国时区 5 if($date_set == ini_get("date.timezone")){ 6 date_default_timezone_set('America/Los_Angeles'); 7 } 8 echo date("Y-m-d H:i:s")."\n"; 9 ?>
获取UNIX时间戳
常用的方法有三种：time(),microtime(),strotime("now")
1 <?php 2 error_reporting(E_ALL ^E_STRICT); 3 echo "time is ".time()."\n"; 4 echo "strotime is ".strtotime("now")."\n"; 5 echo "mktime is ".mktime()."\n"; 6 echo "microtime is ".microtime()."\n"; 7 //参数设置为true返回浮点数表示的时间戳 8 echo "in float microtime is ".microtime(true)."\n"; 9 ?>
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
1 <?php 2 3 //年默认2014 4 echo "mktime(10,10,10,10,12) is ".date("Y-m-d H:i:s",mktime(10,10,10,10,12))."\n"; 5 6 //这种写法会将2014当作月数，年还是默认的2014年 7 echo "mktime(10,10,10,10,2014) is ".date("Y-m-d H:i:s",mktime(10,10,10,10,2014))."\n"; 8 9 echo "mktime(10,10,10,10,32,2014) is ".date("Y-m-d H:i:s",mktime(10,10,10,10,32,2014))."\n"; 10 ?>
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.
1 PHPAPI void php_mktime(INTERNAL_FUNCTION_PARAMETERS, int gmt) 2 { 3 zend_long hou = 0, min = 0, sec = 0, mon = 0, day = 0, yea = 0, dst = -1; 4 timelib_time *now; 5 timelib_tzinfo *tzi = NULL; 6 zend_long ts, adjust_seconds = 0; 7 int error; 8 9 if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "|lllllll", &hou, &min, &sec, &mon, &day, &yea, &dst) == FAILURE) { 10 RETURN_FALSE; 11 } 12 /* Initialize structure with current time */ 13 now = timelib_time_ctor(); 14 if (gmt) { 15 timelib_unixtime2gmt(now, (timelib_sll) time(NULL)); 16 } else { 17 tzi = get_timezone_info(TSRMLS_C); 18 now->tz_info = tzi; 19 now->zone_type = TIMELIB_ZONETYPE_ID; 20 timelib_unixtime2local(now, (timelib_sll) time(NULL)); 21 } 22 /* Fill in the new data */ 23 switch (ZEND_NUM_ARGS()) { 24 case 7: 25 /* break intentionally missing */ 26 case 6: 27 if (yea >= 0 && yea < 70) { 28 yea += 2000; 29 } else if (yea >= 70 && yea <= 100) { 30 yea += 1900; 31 } 32 now->y = yea; 33 /* break intentionally missing again */ 34 case 5: 35 now->d = day; 36 /* break missing intentionally here too */ 37 case 4: 38 now->m = mon; 39 /* and here */ 40 case 3: 41 now->s = sec; 42 /* yup, this break isn't here on purpose too */ 43 case 2: 44 now->i = min; 45 /* last intentionally missing break */ 46 case 1: 47 now->h = hou; 48 break; 49 default: 50 php_error_docref(NULL TSRMLS_CC, E_STRICT, "You should be using the time() function instead"); 51 } 52 /* Update the timestamp */ 53 if (gmt) { 54 timelib_update_ts(now, NULL); 55 } else { 56 timelib_update_ts(now, tzi); 57 } 58 /* Support for the deprecated is_dst parameter */ 59 if (dst != -1) { 60 php_error_docref(NULL TSRMLS_CC, E_DEPRECATED, "The is_dst parameter is deprecated"); 61 if (gmt) { 62 /* GMT never uses DST */ 63 if (dst == 1) { 64 adjust_seconds = -3600; 65 } 66 } else { 67 /* Figure out is_dst for current TS */ 68 timelib_time_offset *tmp_offset; 69 tmp_offset = timelib_get_time_zone_info(now->sse, tzi); 70 if (dst == 1 && tmp_offset->is_dst == 0) { 71 adjust_seconds = -3600; 72 } 73 if (dst == 0 && tmp_offset->is_dst == 1) { 74 adjust_seconds = +3600; 75 } 76 timelib_time_offset_dtor(tmp_offset); 77 } 78 } 79 /* Clean up and return */ 80 ts = timelib_date_to_int(now, &error); 81 ts += adjust_seconds; 82 timelib_time_dtor(now); 83 84 if (error) { 85 RETURN_FALSE; 86 } else { 87 RETURN_LONG(ts); 88 } 89 }
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
1 void timelib_update_ts(timelib_time* time, timelib_tzinfo* tzi) 2 { 3 timelib_sll res = 0; 4 5 do_adjust_special_early(time); 6 do_adjust_relative(time); 7 do_adjust_special(time); 8 res += do_years(time->y); 9 res += do_months(time->m, time->y); 10 res += do_days(time->d); 11 res += do_time(time->h, time->i, time->s); 12 time->sse = res; 13 14 res += do_adjust_timezone(time, tzi); 15 time->sse = res; 16 17 time->sse_uptodate = 1; 18 time->have_relative = time->relative.have_weekday_relative = time->relative.have_special_relative = 0; 19 }
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 - 1) * 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
1 PHP_FUNCTION(strtotime) 2 { 3 char *times, *initial_ts; 4 size_t time_len; 5 int error1, error2; 6 struct timelib_error_container *error; 7 zend_long preset_ts = 0, ts; 8 9 timelib_time *t, *now; 10 timelib_tzinfo *tzi; 11 12 tzi = get_timezone_info(TSRMLS_C); 13 14 if (zend_parse_parameters_ex(ZEND_PARSE_PARAMS_QUIET, ZEND_NUM_ARGS() TSRMLS_CC, "sl", ×, &time_len, &preset_ts) != FAILURE) { 15 /* We have an initial timestamp */ 16 now = timelib_time_ctor(); 17 18 initial_ts = emalloc(25); 19 snprintf(initial_ts, 24, "@" ZEND_LONG_FMT " UTC", preset_ts); 20 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 */ 21 timelib_update_ts(t, tzi); 22 now->tz_info = tzi; 23 now->zone_type = TIMELIB_ZONETYPE_ID; 24 timelib_unixtime2local(now, t->sse); 25 timelib_time_dtor(t); 26 efree(initial_ts); 27 } else if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|l", ×, &time_len, &preset_ts) != FAILURE) { 28 /* We have no initial timestamp */ 29 now = timelib_time_ctor(); 30 now->tz_info = tzi; 31 now->zone_type = TIMELIB_ZONETYPE_ID; 32 timelib_unixtime2local(now, (timelib_sll) time(NULL)); 33 } else { 34 RETURN_FALSE; 35 } 36 37 if (!time_len) { 38 timelib_time_dtor(now); 39 RETURN_FALSE; 40 } 41 42 t = timelib_strtotime(times, time_len, &error, DATE_TIMEZONEDB, php_date_parse_tzfile_wrapper); 43 error1 = error->error_count; 44 timelib_error_container_dtor(error); 45 timelib_fill_holes(t, now, TIMELIB_NO_CLONE); 46 timelib_update_ts(t, tzi); 47 ts = timelib_date_to_int(t, &error2); 48 49 timelib_time_dtor(now); 50 timelib_time_dtor(t); 51 52 if (error1 || error2) { 53 RETURN_FALSE; 54 } else { 55 RETURN_LONG(ts); 56 } 57 }
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]*[0-9]+); 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, 24); timelib_eat_spaces((char **) &ptr); timelib_set_relative((char **) &ptr, i, 1, 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 = 1; while (((**ptr < '0') || (**ptr > '9')) && (**ptr != '+') && (**ptr != '-')) { if (**ptr == '\0') { return TIMELIB_UNSET; } ++*ptr; } while (**ptr == '+' || **ptr == '-') { if (**ptr == '-') { dir *= -1; } ++*ptr; } return dir * timelib_get_nr(ptr, max_length); }
1 static void timelib_set_relative(char **ptr, timelib_sll amount, int behavior, Scanner *s) 2 { 3 const timelib_relunit* relunit; 4 5 if (!(relunit = timelib_lookup_relunit(ptr))) { 6 return; 7 } 8 9 switch (relunit->unit) { 10 case TIMELIB_SECOND: s->time->relative.s += amount * relunit->multiplier; break; 11 case TIMELIB_MINUTE: s->time->relative.i += amount * relunit->multiplier; break; 12 case TIMELIB_HOUR: s->time->relative.h += amount * relunit->multiplier; break; 13 case TIMELIB_DAY: s->time->relative.d += amount * relunit->multiplier; break; 14 case TIMELIB_MONTH: s->time->relative.m += amount * relunit->multiplier; break; 15 case TIMELIB_YEAR: s->time->relative.y += amount * relunit->multiplier; break; 16 17 case TIMELIB_WEEKDAY: 18 TIMELIB_HAVE_WEEKDAY_RELATIVE(); 19 TIMELIB_UNHAVE_TIME(); 20 s->time->relative.d += (amount > 0 ? amount - 1 : amount) * 7; 21 s->time->relative.weekday = relunit->multiplier; 22 s->time->relative.weekday_behavior = behavior; 23 break; 24 25 case TIMELIB_SPECIAL: 26 TIMELIB_HAVE_SPECIAL_RELATIVE(); 27 TIMELIB_UNHAVE_TIME(); 28 s->time->relative.special.type = relunit->multiplier; 29 s->time->relative.special.amount = amount; 30 } 31 }
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。
1 <?php 2 3 /** 4 * process date 5 * @author huntstack 6 * @time 2014-10-18 7 */ 8 class Process_Date{ 9 10 private $date; 11 private $M,$D,$Y; 12 13 /** 14 * set the date for next operator 15 * @parameter date:time string or timestamp 16 */ 17 function __construct($date=""){ 18 if($date == "" || empty($date)){ 19 $this->date = strtotime("now"); 20 }else if(gettype($date) == "string"){ 21 $this->date = strtotime($date); 22 }else if(gettype($date) == "integer"){ 23 $this->date = $date; 24 }else{ 25 throw new Exception("paramter must be timestamp or date string or empty for current time"); 26 } 27 $this->set_varibales(); 28 } 29 30 public function set_date($date){ 31 $this->date = strtotime($date); 32 $this->set_varibales(); 33 } 34 35 private function set_varibales(){ 36 $this->M = date("m",$this->date); 37 $this->D = date("d",$this->date); 38 $this->Y = date("Y",$this->date); 39 } 40 41 /** 42 * get the specified weeks 43 * @parameter $i:numbers of week 44 * @parameter $flag:0->last,1->next 45 */ 46 public function get_week($i=0,$flag=1){ 47 if($flag == 0) return date("YW",strtotime("-$i week",$this->date)); 48 else if($flag == 1) return date("YW",strtotime("+$i week",$this->date)); 49 } 50 51 /** 52 * get the specified months 53 * @parameter $i:numbers of month 54 * @parameter $flag:0->last,1->next 55 */ 56 public function get_month($i=0,$flag=1){ 57 if($flag == 0) return date("Y-m",mktime(0,0,0, $this->M-$i, 1, $this->Y)); 58 else if($flag == 1) return date("Y-m",mktime(0,0,0, $this->M+$i, 1, $this->Y)); 59 } 60 61 /** 62 * get the specified days 63 * @parameter $i:numbers of day 64 * @parameter $flag:0->last,1->next 65 */ 66 public function get_day($i=0,$flag=1){ 67 if($flag == 0) return date("Y-m-d",mktime(0,0,0, $this->M, $this->D-$i, $this->Y)); 68 else if($flag == 1) return date("Y-m-d",mktime(0,0,0, $this->M, $this->D+$i, $this->Y)); 69 } 70 71 /** 72 * get the last $count days 73 * @parameter count:number 74 */ 75 public function get_last_days($count){ 76 $return = array(); 77 for($i=1;$i<=$count;$i++){ 78 array_push($return, $this->get_day($i,0)); 79 } 80 return $return; 81 } 82 83 /** 84 * get the next $count days 85 * @parameter count:number 86 */ 87 public function get_next_days($count){ 88 $return = array(); 89 for($i=1;$i<=$count;$i++){ 90 array_push($return, $this->get_day($i,1)); 91 } 92 return $return; 93 } 94 95 /** 96 * get the last $count weeks 97 * @parameter count:number 98 */ 99 public function get_last_weeks($count){ 100 $return = array(); 101 for($i=1;$i<=$count;$i++){ 102 array_push($return, $this->get_week($i,0)); 103 } 104 return $return; 105 } 106 107 /** 108 * get the next $count weeks 109 * @parameter count:number 110 */ 111 public function get_next_weeks($count){ 112 $return = array(); 113 for($i=1;$i<=$count;$i++){ 114 array_push($return, $this->get_week($i,1)); 115 } 116 return $return; 117 } 118 119 /** 120 * get the last $count months 121 * @parameter count:number 122 */ 123 public function get_last_month($count){ 124 $return = array(); 125 for($i=1;$i<=$count;$i++){ 126 array_push($return, $this->get_month($i,0)); 127 } 128 return $return; 129 } 130 131 /** 132 * get the next $count months 133 * @parameter count:number 134 */ 135 public function get_next_month($count){ 136 $return = array(); 137 for($i=1;$i<=$count;$i++){ 138 array_push($return, $this->get_month($i,1)); 139 } 140 return $return; 141 } 142 143 /** 144 * get the first day and the last day of a week 145 */ 146 public function get_week_begin_end(){ 147 $return["begin"] = mktime(0,0,0, $this->M, $this->D-date("w",$this->date)+1, $this->Y); 148 $return["end"] = mktime(23,59,59, $this->M, $this->D-date("w",$this->date)+7, $this->Y); 149 return $return; 150 } 151 152 /** 153 * get the first day and the last day of a month 154 */ 155 public function get_month_begin_end(){ 156 $return["begin"] = strtotime("first day of",$this->date); 157 $return["end"] = strtotime("last day of",$this->date); 158 return $return; 159 } 160 } 161 ?>
参考资料：
1.http://php.net/manual/zh/book.datetime.php
2.http://www.phppan.com/2011/06/php-strtotime/