<?php

$result = '{"english":{"grade":"7","time":"79"},"physics":{"grade":"3","time":"48"}}';
$JSONResult = json_decode($result, true); // to get an associative array rather than objects
foreach ($JSONResult as $subjectKey => $aSubject) {
    $userResult = "
        Subject: $subjectKey
        Grade: {$aSubject['grade']}
        Time: {$aSubject['time']}
    ";
    echo $userResult;
}