How to get json format below in php - php

Question

I am New to PHP I want to generate a json code like this
[{"section_name": "Section A","data": [{"value": "2"},{"value": "0"}]}, {"section_name": "Section B","data": [{"value": "1"},{"value": "0"}]}]
In this I am retrieving "section_name","value" from database.
Here the concept is get values from database to display a bar chart, based on classes and sections.
But my template I had chosen, I have to get the values(no. of students in a class & section) for individual sections, as shown in below bar chart.
My PHP Code:
$result1 = mysql_query("select class_name as label from class ") or die(mysql_error());
while($row1 = mysql_fetch_assoc($result1))
{
$rows1[] = $row1;
}
$data1 = json_encode($rows1);
$result2 = mysql_query("select s.section_name as sectionname, 'data' as data from section s") or die(mysql_error());
$result3 = mysql_query("select (select count(*)as c from student_status ss where ss.section_id=s.section_id and ss.class_id=c.class_id) as value from section s, class c order by s.section_name asc ") or die(mysql_error());
if(mysql_num_rows($result2) > 1)
{
while($row2 = mysql_fetch_assoc($result2))
{
$rows2[] = $row2;
}
$data2 = json_encode($rows2);
while($row3 = mysql_fetch_assoc($result3))
{
$rows3[] = $row3;
}
$data3 = json_encode($rows3);
}
My JSON CODE:
"categories": [
{
"category": <? echo $data1 ?>/*[
{
"label": "1"
},
{
"label": "TWO"
},
{
"label": "3"
}
]*/
}
],
"dataset": /*<? echo $data2 ?>*/[
{
"sectionname": "Section A",
"data": [
{
"value": "2" //class 1
},
{
"value": "1" //class 2
}
]
},
{
"sectionname": "Section B",
"data": [
{
"value": "" //class 1
},
{
"value": "" //class2
}
]
}
]
Hope you guys understand question.

Answer 1

If you are new with php, you should read array in php manual.
Then you can define an array like this
$arr = array(
array(
'section_name' => 'Section A',
'data => array(
array('value' => 2),
array('value' => 0),
)
),
)
//... other section
Then output json echo json_encode($arr);

Answer 2

[] is used for array and {"a": ..} for associative arrays. Combining this two together and you could easily create this json structure.
array(
array(
"section_name" => "Section A",
"data" => array(
array("value" => "2"),
array("value" => "0"),
)
),
// ...
)
Using json_encode gives you the wanted result.