<?php

$results = [
    ['name' => '田中',  'japanese' => 83, 'math' => 57, 'science' => 43,  'social' => 72, 'english' => 78],
    ['name' => '渡部',  'japanese' => 62, 'math' => 88, 'science' => 70,  'social' => 66, 'english' => 38],
    ['name' => '品川',  'japanese' => 23, 'math' => 33, 'science' => 53,  'social' => 17, 'english' => 7],
    ['name' => '滝谷',  'japanese' => 93, 'math' => 89, 'science' => 79,  'social' => 96, 'english' => 91],
    ['name' => '川原田','japanese' => 55, 'math' => 56, 'science' => 60,  'social' => 54, 'english' => 66],
    ['name' => '一色',  'japanese' => 27, 'math' => 47, 'science' => 100, 'social' => 42, 'english' => 38],
];

function cmp($asc, $desc){
    return ($asc['japanese'] <=> $desc['japanese'] );
}
usort($results, "cmp");

var_dump($results);
?>

<?php

function cmp($asc, $desc){
    return ($desc['japanese'] <=> $asc['japanese'] );
}
usort($results, "cmp");

var_dump($results);
?>