Iterating through a column in a CSV file (PHP) - php

Question

I need to write a function that takes a year and a temperature as an input and returns how many days in a given year the temperature was equal to or below the given temperature. Since the data is about hours, not days, need to find the number of hours and divide it by 24.
Example: getDaysUnderTemp(2019, -10) returns 13.92.
CSV file looks like this (year, month, day, hour, temperature):
2019,1,1,0,0.1
2019,1,1,1,0.4
2019,1,1,2,0.8
2019,1,1,3,1.3
2019,1,1,4,1.8
...
2020,1,1,0,-3.9
So far my code looks like this (I'm new to php):
function getDaysUnderTemp(int $targetYear, float $targetTemp): float {
$inputFile = fopen("data/temperatures-debug.csv", "r");
while (!feof($inputFile)) {
$file = fgetcsv($inputFile);
$hours = intval($file[3]);
if (intval($file[0]) === $targetYear and floatval($file[4]) <= $targetTemp) {
???
return ??? / 24;
}
fclose($inputFile);
}
return "error";
}
The problem is I don't know how to iterate through a column which represents the hours of a specific year, and then add them all together.

Answer 1

you are not far from the solution.
function getDaysUnderTemp($targetYear, $targetTemp): float
{
$hours = 0;
if ((($handle = fopen("data.csv", "r")) !== FALSE)) {
while (($data = fgetcsv($handle)) !== FALSE) {
// [0] -> year [1] -> month [2] -> day [3] -> hours [4] -> temp
if ($data[0] == $targetYear && $data[4] <= $targetTemp) {
$hours += $data[3];
}
}
fclose($handle);
}
return $hours / 24;
}
The logic you had was correct, I just refactored the code and fixed some small issues:
Your function is bound to return a float value but since in your code you are returning the string "error" when a match is not found It would have thrown an exception at some point. I am now returning $hours / 24 so now the problem is solved;
After each iteration, you close the pointer to file by calling fclose($inputFile), this can cause some problems since the feof function needs a valid stream not closed to work properly. Now the fclose function is called only once when the work is done;
For printing the results I suggest you to use the printf function as follows:
printf("%.2f", getDaysUnderTemp(2019, -10);