Obtaining JSON data with foreach in PHP - php

Question

A site contains monthly data in a JSON format. This can be queried like so:
http://www.example.com?startdate=1-1-1985&enddate=31-1-1985
I want to be able to run a script that will obtain the specific data I am looking for, starting from today's month, then work backward until null data is returned. Each month's value needs to add up. So far, this is what I've got:
//Build base URL:
$userid=$_GET['userid'];
$startdate=/*Beginning of today's month*/;
$enddate=/*End of today's month*/;
$url='http://www.example.com?userid='.$userid.'&startdate='.$startdate.'&enddate='.$enddate;
//Set JSON variables:
$get=file_get_contents($url);
$json=json_decode($get);
//Set loop variables:
$value=0;
$month=0;
/*For each month from today backwards{
$number=$json->integer;
if($number!=null){
$value=$value+$number;
$month=$month+1;
}else{
break;
}
}
echo $value;
echo $month;
*/
The part I'm having problems with is the beginning of the fourth part. How do I run a loop that starts with the range of today's month, obtain $number, then repeat with the previous month, until it reaches a month that returns null?

Answer 1

You could use the DateTime object and it's associated methods ( specifically sub in this case ) to count backwards by subtracting 1month at a time. An array stores the months/dates and the url is constructed using the variable counter $i
Initially this has a maximum backwards range of 20years ( which I guessed would be more than enough ) but it's easy to change.
$df='Y-m-d';
$userid=$_GET['userid'];
$timezone=new DateTimeZone('Europe/London');
$interval=new DateInterval('P1M');
$ts=date( $df, strtotime( date('Y-m-1') ) );
$tf=date( $df, strtotime( date('Y-m-1'). ' - 20 years') );
$start=new DateTime( $ts, $timezone );
$end=new DateTime( $tf, $timezone );
$dates=array();
$i=0;
while( $start->sub( $interval ) > $end ){
$dates[]=$start->format( $df );
if( $i > 1 ){
$startdate=$dates[ $i - 1 ];
$enddate=$dates[ $i ];
$url='http://www.example.com?userid='.$userid.'&startdate='.$startdate.'&enddate='.$enddate;
echo $url,'<br />';
/* uncomment when happy with mechanism */
/*
$data=file_get_contents( $url );
if( $data ) ) {
$json=json_decode( $data );
#process.....
break;
}
*/
}
$i++;
}
A snippet of the output
http://www.example.com?userid=bobodaclown&startdate=2017-10-01&enddate=2017-09-01
http://www.example.com?userid=bobodaclown&startdate=2017-09-01&enddate=2017-08-01
http://www.example.com?userid=bobodaclown&startdate=2017-08-01&enddate=2017-07-01
http://www.example.com?userid=bobodaclown&startdate=2017-07-01&enddate=2017-06-01
http://www.example.com?userid=bobodaclown&startdate=2017-06-01&enddate=2017-05-01
http://www.example.com?userid=bobodaclown&startdate=2017-05-01&enddate=2017-04-01
http://www.example.com?userid=bobodaclown&startdate=2017-04-01&enddate=2017-03-01

Answer 2

By using strtotime() and mktime() functions you can while loop until you get Null results. The below code will print 5 urls for 5 months. Change while condition accordingly.
// define $i
$i=0;
$userid = '343';//$_GET['userid']; //dont forget to replace with userid
do{
$timestring = strtotime("now -$i month");
//get Month
$month = date('m',$timestring);
//get Year
$year = date('Y',$timestring);
// First date Month and Year
$startdate = date('d-m-Y', mktime(0, 0, 0, $month, 1, $year));
// Last date Month and Year
$enddate = date('d-m-Y', mktime(0, 0, 0, $month+1, 0,$year));
$url='http://www.example.com?userid='.$userid.'&startdate='.$startdate.'&enddate='.$enddate;
// commenting your code
//Set JSON variables:
//$get=file_get_contents($url);
//$json=json_decode($get);
// $number=$json->integer;
echo $url;
echo "\n";
$i++;
}while ($i!=5); // change while condition according to your requirement. while ($number!=null)
Out Put:
http://www.example.com?userid=343&startdate=01-12-2017&enddate=31-12-2017
http://www.example.com?userid=343&startdate=01-11-2017&enddate=30-11-2017
http://www.example.com?userid=343&startdate=01-10-2017&enddate=31-10-2017
http://www.example.com?userid=343&startdate=01-09-2017&enddate=30-09-2017
http://www.example.com?userid=343&startdate=01-08-2017&enddate=31-08-2017