php array to json sting conversion - php

Question

Hi every one i am pretty new to programming and my worry is as follows.
I have the following php code where students' averages are calculated and the result filled in an asssociative array. This array should later on be converted to json format.
require_once("functions.inc"); // all my functions are here
$conn = mysqli_connect(DBHOST,DBUSER,DBPASS,DB); // connects to my database
if (!$conn) {
error_log("Cannot connect to MySQL: " .$mysqli->connect_error);
return false;
}
$query = "SELECT distinct exam.student_matricule from exam join student on exam.student_matricule=student.student_matricule where student.class_id=3"; //
$result=mysqli_query($conn,$query);
if(false===$result)
{
printf("error: %s \n",mysqli_error($conn));
}
while($row= $result->fetch_assoc())
{
$studentmatricule = $row['student_matricule'];
$average=student_average(3,$studentmatricule,1); // this function call calculates students' averages
$stud_averages[$studentmatricule]=$average; //associative array that has **$studentmatricule** as key and **$average** as value
}
foreach($stud_averages as $student => $av)
{
$data=array('student_matricule'=>"$student",'average'=>"$av");
print json_encode($data);
}
My worry now is, print json_encode($data) prints
{"student_matricule":"17A002NA","average":"12.52"}{"student_matricule":"17A001NA","average":"10.53"}{"student_matricule":"17A003NA","average":"12.69"}
But i want something like
[{"student_matricule":"17A002NA","average":"12.52"},{"student_matricule":"17A001NA","average":"10.53"},{"student_matricule":"17A003NA","average":"12.69"}]
Please what should i do?
Thanks in advance!

Answer 1

You're printing single dimensional Array inside loop so it is printing as a JSON
If you want it as a JSON array you need to store it in a multidimensional array like this
$data = [];
foreach($stud_averages as $student => $av)
{
$data[]=array('student_matricule'=>"$student",'average'=>"$av");
}
print json_encode($data); // It prints JSON Array

Answer 2

You are printing every array seperately in foreach loop. You need to add every loop data in a array that defined outside the loop. You can try like this :
$res = array();
foreach($stud_averages as $student => $av)
{
$data=array('student_matricule'=>"$student",'average'=>"$av");
array_push($res, $data);
}
print json_encode($res);

Answer 3

you can also try like this
$data = [];
$std = array();
foreach($stud_averages as $student => $av)
{
$std['student_matricule']= "$student";
$std['average'] ="$av";
}
array_push($data,$std);
print json_encode($data); // It prints JSON Array