PHP と PDO: データベース内の日付と時刻を処理する方法

<?php
$host = 'localhost';
$dbname = 'test';
$username = 'root';
$password = '';

try {
    $conn = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);
    echo "Connected to database successfully!";
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>

<?php
$date = date("Y-m-d");
$time = date("H:i:s");
$datetime = date("Y-m-d H:i:s");

$stmt = $conn->prepare("INSERT INTO table_name (date_column, time_column, datetime_column) VALUES (?, ?, ?)");
$stmt->bindParam(1, $date);
$stmt->bindParam(2, $time);
$stmt->bindParam(3, $datetime);

if ($stmt->execute()) {
    echo "Data inserted successfully!";
} else {
    echo "Data insertion failed!";
}
?>

<?php
$stmt = $conn->prepare("SELECT date_column, time_column, datetime_column FROM table_name");
$stmt->execute();
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);

foreach ($result as $row) {
    $date = date("Y-m-d", strtotime($row['date_column']));
    $time = date("H:i:s", strtotime($row['time_column']));
    $datetime = date("Y-m-d H:i:s", strtotime($row['datetime_column']));

    echo "Date: $date, Time: $time, DateTime: $datetime<br>";
}
?>

<?php
$newDate = date("Y-m-d", strtotime("2022-01-01"));
$newTime = date("H:i:s", strtotime("15:30:00"));
$newDatetime = date("Y-m-d H:i:s", strtotime("2022-01-01 15:30:00"));

$stmt = $conn->prepare("UPDATE table_name SET date_column = ?, time_column = ?, datetime_column = ?");
$stmt->bindParam(1, $newDate);
$stmt->bindParam(2, $newTime);
$stmt->bindParam(3, $newDatetime);

if ($stmt->execute()) {
    echo "Data updated successfully!";
} else {
    echo "Data update failed!";
}
?>