Obtain the start date of the week based on the given date format 'yyyy-mm-DD'-PHP source code

Obtain the php code for the start date of the week based on the given date format YYYY-mm-dd.

/*** Get the start date of all weeks in a year * @ param $ year format 'yyyy' * returns the two-dimensional array subscript key1 value corresponding to the actual year key2 value of the week in a year week number of a day in a year [week of the year] * return false date format error */function get_all_weeks ($ year) {$ week_arr = array (); $ year = intval (trim ($ year); $ preg = "/^ \ d {4, }$/"; if (! Preg_match ($ preg, $ year) {return false;} $ begin_day = $ year. '-01-01'; $ end_day = $ year. '-12-31'; // The first Monday of the year if (date ('W', strtotime ($ begin_day ))! = 1) {$ begin_day = date ('Y-m-D', strtotime ("next Monday", strtotime ($ begin_day )));} // week number of the first Monday $ begin_week_num = intval (date ('W', strtotime ($ begin_day); // if (date ('W ', strtotime ($ end_day ))! = 0) {$ end_day = date ('Y-m-D', strtotime ("last Sunday", strtotime ($ end_day); // There is a week across the year, monday of the New Year's week $ end_day_next = date ('Y-m-D', strtotime ($ end_day) + 24*60*60 ); // year and week of the new year $ stride_year = date ('O', strtotime ($ end_day_next); $ stride_weeknum = intval (date ('W ', strtotime ($ end_day_next);} // The number of weeks of the last Sunday $ end_week_num = intval (date ('W', strtotime ($ end_day ))); // The first Monday of a year is the first week of a year or the second week if ($ begin_week_num! = 1) {$ I = 2;} else {$ I = 1;} $ j = 0; for ($ I; $ I <= $ end_week_num; $ I ++) {$ start_date = date ("Y-m-d", strtotime ("$ begin_day $ j week"); $ end_day = date ("Y-m-d ", strtotime ($ start_date. '+ 6 Day'); $ week_arr [$ year] [$ I] = array ($ start_date, $ end_day); $ j ++;} if ($ end_day_next) {$ week_arr [$ stride_year] [$ stride_weeknum] = array ($ end_day_next, date ("Y-m-d", strtotime ($ end_day_next. '+ 6 Day');} return $ w Eek_arr;} // demo _ call/* $ year = '000000'; if (get_all_weeks ($ year) {var_dump (get_all_weeks ($ year ));} else {echo 'date format error ';} * // *** get the start date of the week in which a day is located * depends on function get_all_weeks * @ param $ day format: 'yyyy-mm-DD' * returns false date format error *, returns json "{" begin_day ":" YYYY-mm-dd "," end_day ": "YYYY-mm-dd"} "*/function get_day_week ($ day) {$ date_arr = explode ('-', trim ($ day); if (! Checkdate (intval ($ date_arr [1]), intval ($ date_arr [2]), intval ($ date_arr [0]) {return false ;} $ year = date ('Y', strtotime ($ day); $ weeks = get_all_weeks ($ year ); // year and week of a day $ real_year = date ('O', strtotime ($ day); $ week_num = intval (date ('W ', strtotime ($ day); if (! Empty ($ weeks [$ real_year] [$ week_num] [0]) $ begin_day = $ weeks [$ real_year] [$ week_num] [0]; if (! Empty ($ weeks [$ real_year] [$ week_num] [1]) $ end_day = $ weeks [$ real_year] [$ week_num] [1]; // the cross-year week value is stored in the if (empty ($ begin_day) | empty ($ end_day) {$ year = date ('Y', strtotime ($ day) of the previous year )) -1; $ weeks = get_all_weeks ($ year); $ real_year = date ('O', strtotime ($ day); $ week_num = intval (date ('W ', strtotime ($ day); if (! Empty ($ weeks [$ real_year] [$ week_num] [0]) $ begin_day = $ weeks [$ real_year] [$ week_num] [0]; if (! Empty ($ weeks [$ real_year] [$ week_num] [1]) $ end_day = $ weeks [$ real_year] [$ week_num] [1];} $ the_day = array ('In in _ day' => $ begin_day, 'end _ day' => $ end_day); $ the_day = json_encode ($ the_day); return $ the_day ;} // demo _ call/* $ day = '2017-01-01 '; if (get_day_week ($ day) {var_dump (get_day_week ($ day ));} else {echo 'date format error ';}*/