Fill missing array elements with zero values for Flot - php

Question

I'm creating an array in PHP to send back to the front end for display in a Flot line chart. I have data that should be displayed year to date by month. If my SQL statement doesn't find any values for a given month, there is no array element for that month, and the Flot chart doesn't plot a data point for that month (See Mar and Apr in screenshot below). I'd like it to show a zero data point for months where there is no data.
Here's how I'm creating my array:
$array = array();
$array['data'] = Array();
$array['label'] = $tags[0]['tag_name'];
foreach($tags as $key=>$value) {
$month = $value['month'];
$arr = Array($month, $value['trans_amount']);
array_push($array['data'], $arr);
}
Current output:
{"data":[[1,"75.00"],[2,"170.00"],[5,"100.00"]],"label":"example label"}
Desired output:
{"data":[[1,"75.00"],[2,"170.00"],[3, "0"],[4, "0"],[5,"100.00"]],"label":"example label"}
and here's how the chart currently displays with the current output:

Answer 1

This works. It's a slight modification of your foreach loop. You need an extra variable $monthVal keep track of the current month.
//Assuming this the month uptil which you want the data.
$current_month = 7;
$monthVal = 1;
foreach($tags as $key=>$value) {
$month = $value['month'];
if($month != $monthVal){
while($month != $monthVal){
$array['data'][] = Array($monthVal, "0");
$monthVal += 1;
}
}
$arr = Array($month, $value['trans_amount']);
array_push($array['data'], $arr);
$monthVal += 1;
}
//This loop is added to append the array if the last entry is not equal to $current_month.
while($monthVal <= $current_month){
$array['data'][] = Array($monthVal, "0");
$monthVal += 1;
}

Answer 2

This should work. What I do is check if there is a missing months and then populate that month with zero as value.
$currMonth = 1;
foreach($tags as $key=>$value) {
$month = $value['month'];
if($month != $currMonth){
//if we are missing some months populate that month with zero as value
while($month != $currMonth){
array_push($array['data'],Array($currMonth, "0"));
$currMonth++;
}
}
$arr = Array($month, "'" . $value['trans_amount'] . "'");
array_push($array['data'], $arr);
$currMonth++;
}
echo json_encode($array);

Answer 3

I would change your SQL query to return more data, if it is stored as a date.
Try to maintain dates as dates rather than integers. PHP and SQL date functions are extensive and useful.
This simple for loop will fill the array with the missing data from the SQL query before the foreach.
for($i=1;$i<=12;$i++){
if(!isset($tags[$i])){
$tags[$i]['month'] = $i;
$tags[$i]['trans_amount'] = 0;
}
}
foreach($tags as $key=>$value) {
$month = $value['month'];
$arr = array($month, $value['trans_amount']);
array_push($array['data'], $arr);
}

Answer 4

Try this (works in PHP 5.3+):
$array = array();
$month_min = $month_max = 0;
foreach($tags as $value) {
$month = $value['month'];
$array[$month - 1] = array($month, $value['trans_amount']);
$month_max = $month;
if (!$month_min) $month_min = $month;
}
$months = array_values(array_map(function ($v) { return intval($v['month']); }, $tags));
$months_range = range(1, $month_max);
foreach (array_diff($months_range, $months) as $month) {
$array[$month - 1] = array($month, 0);
}
$result = array(
'data' => array_slice($array, $month - 1),
'label' => $tags[0]['tag_name'],
);
print_r(json_encode($result));