php多维数组排序以及实际工作中的应用

    <meta charset="utf-8">
    <title>Sorting Multidimensional Arrays</title>


<?php $a = [
    [
        'key1' => 940,
        'key2' => 'blah',
    ],
    [
        'key1' => 23,
        'key2' => 'this',
    ],
    [
        'key1' => 894,
        'key2' => 'that',
    ],
];

var_dump($a);
// 比较的规则第一个小于第二个返回负数或false, 相当于第一个的值减去第二个, 如果前小后大则为负, 前大后小则为正, 两个一样, 则为0

//按第一个数组key1的数字从小到大排序
function asc_number_sort($x, $y) {
    echo "iteration x1 = ".$x['key1'].' y = '.$y['key1'];
    if ($x['key1'] > $y['key1']) {
        return true; // true或正数表示第二个参数应该排在前面, 小的在前
    } elseif ($x['key1']  ["name" => "Name", "grade" => xx.x];

    $students = [
        256 => ['name' => 'Jon', 'grade' => '98.5'],
        2 => ['name' => 'Vance', 'grade' => '85.1'],
        9 => ['name' => 'Stephen', 'grade' => '94.0'],
        364 => ['name' => 'Steve', 'grade' => '85.1'],
        68 => ['name' => 'Rob', 'grade' => '74.6'],
    ];

    function name_sort($x, $y) {
        return strcasecmp($x['name'], $y['name']);
    }

    function grade_sort($x, $y) {
        return $x['grade'] 

    <meta charset="utf-8">
    <title>Sorting Multidimensional Arrays</title>


<?php $db = mysqli_connect('192.168.31.172', 'root', 'root', 'phpadvanced');
mysqli_query($db, "set names utf8");

if(!empty($_POST['task'])) {
    $parent_id = 0;
    if(isset($_POST['parent_id']) && filter_var($_POST['parent_id'], FILTER_VALIDATE_INT, ['min_range' => 1])) {
        $parent_id = $_POST['parent_id'];
    }

    $task = mysqli_real_escape_string($db, strip_tags($_POST['task']));

    $q = "INSERT INTO tasks (parent_id, task) VALUES ($parent_id, '$task')";
    echo $q;
    $r = mysqli_query($db, $q);

    if(mysqli_affected_rows($db) == 1) {
        echo '<p>任务添加成功</p>';
    } else {
        echo '<p>任务添加失败</p>';
    }
}
?>
    

CREATE TABLE tasks (
  task_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
  parent_id INT UNSIGNED NOT NULL DEFAULT 0,
  task VARCHAR(100) NOT NULL,
  date_added TIMESTAMP NOT NULL,
  date_completed TIMESTAMP,
  PRIMARY KEY (task_id),
  INDEX parent (parent_id),
  INDEX added (date_added),
  INDEX completed (date_completed)
);