如何使用php直接从json文件访问值

Question

Currently I have the following code.

<?php
$jsonFP = '[{"Maths":{"earlierMarks":85,"currMarks":90}},{"Physics":{"earlierMarks":80,"currMarks":85}},{"Science":{"earlierMarks":82,"currMarks":85}},{"Social":{"earlierMarks":75,"currMarks":60}}]';

$histData=json_decode($jsonFP,true);
print_r($histData);
$subject_list = array("Social","Maths","Physics");

foreach($subject_list as $subject){
        print_r($histData[$subject]);
        echo "
";
}
?>

But this print_r($histData[$subject]); statement expects index like this print_r($histData[some index][$subject]);

How can I access the values in $histData dynamically while looping for $subject_list

Answer 1

If you're alright with changing your input ($jsonFP), you can restructure it to remove the array and have it just be an object:

$jsonFP = '{"Maths":{"earlierMarks":85,"currMarks":90},"Physics":{"earlierMarks":80,"currMarks":85},"Science":{"earlierMarks":82,"currMarks":85},"Social":{"earlierMarks":75,"currMarks":60}}';

$histData = json_decode($jsonFP, true);

echo $histData['Maths']['earlierMarks']; // prints 85
echo $histData['Social']['currMarks']; // prints 60

Because you no longer have an array, you can access the elements in it without needing the numbered index.