PHP: JSON and Email

Q: Should I use mail() or an SMTP library?

mail() is convenient for local dev (if configured). Use an SMTP library (PHPMailer) in production—it has better error handling, supports attachments, multiple recipients, and isn't affected by server mail configuration.

JSON is the universal language of the web—frontend-backend communication depends on it, API data transfer uses it, and even config files are written in it. Email is a must-have feature for any web application—registration verification, password resets, and notifications. This lesson covers both.

1. JSON Basics

PHP

<?php
// PHP array/object → JSON string
$data = [
    'name' => 'John',
    'age'  => 25,
    'skills' => ['PHP', 'MySQL', 'JavaScript'],
    'isActive' => true,
    'score' => null,
];

$json = json_encode($data);
echo $json;
// {"name":"John","age":25,"skills":["PHP","MySQL","JavaScript"],"isActive":true,"score":null}
?>

(1) Common json_encode Options

PHP

<?php
$data = ['name' => 'John', 'age' => 25, 'score' => null];

// Pretty print (human-readable)
echo json_encode($data, JSON_PRETTY_PRINT);
/*
{
    "name": "John",
    "age": 25,
    "score": null
}
*/

// Don't escape Unicode (preserves non-ASCII characters)
echo json_encode($data, JSON_UNESCAPED_UNICODE);
// {"name":"John","age":25,"score":null}

// Combine options
echo json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);

// Handle null (PHP 8.3+)
echo json_encode($data, JSON_UNESCAPED_UNICODE, JSON_INVALID_UTF8_IGNORE);
?>

Option	Effect
`JSON_PRETTY_PRINT`	Indented formatting
`JSON_UNESCAPED_UNICODE`	Don't escape non-ASCII to `\uXXXX`
`JSON_UNESCAPED_SLASHES`	Don't escape `/` to `\/`
`JSON_NUMERIC_CHECK`	Convert numeric strings to numbers
`JSON_FORCE_OBJECT`	Output `{}` for empty arrays

2. json_decode — Parsing JSON

PHP

<?php
$json = '{"name":"John","age":25,"skills":["PHP","MySQL"]}';

// Default: returns an object
$obj = json_decode($json);
echo $obj->name;  // John
echo $obj->skills[0];  // PHP

// Second parameter true → returns an associative array
$arr = json_decode($json, true);
echo $arr['name'];  // John

// Error handling
$badJson = '{name: John}';  // Missing double quotes
$result = json_decode($badJson);
if (json_last_error() !== JSON_ERROR_NONE) {
    echo "JSON parse error: " . json_last_error_msg();
    // JSON parse error: Syntax error
}

// PHP 7.3+ cleaner syntax
$result = json_decode($badJson);
echo json_last_error_msg();
?>

▶ サンプル: Reading and Writing JSON Files

PHP

<?php
// === Writing a JSON File ===
$config = [
    'app_name' => 'MyBlog',
    'version'  => '1.2.0',
    'database' => [
        'host' => 'localhost',
        'name' => 'myblog',
    ],
    'features' => ['blog', 'comments', 'search'],
];

$json = json_encode($config, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
file_put_contents('config.json', $json, LOCK_EX);
echo "Config file written ✅";

// === Reading a JSON File ===
$json = file_get_contents('config.json');
$config = json_decode($json, true);

echo "App name: {$config['app_name']}<br>";
echo "Database host: {$config['database']['host']}<br>";
echo "Features: " . implode(', ', $config['features']) . "<br>";
?>

▶ 試してみよう

▶ サンプル: REST API Simulation

PHP

<?php
// api.php — simple JSON API
header('Content-Type: application/json; charset=utf-8');

$method = $_SERVER['REQUEST_METHOD'];
$path = $_GET['path'] ?? '';

$users = [
    ['id' => 1, 'name' => 'John', 'email' => 'j@j.com'],
    ['id' => 2, 'name' => 'Jane', 'email' => 'ja@ja.com'],
];

if ($method === 'GET' && $path === 'users') {
    echo json_encode(['status' => 'ok', 'data' => $users], JSON_UNESCAPED_UNICODE);
} elseif ($method === 'GET' && preg_match('/users\/(\d+)/', $path, $m)) {
    $id = (int)$m[1];
    $user = $users[$id - 1] ?? null;
    if ($user) {
        echo json_encode(['status' => 'ok', 'data' => $user], JSON_UNESCAPED_UNICODE);
    } else {
        http_response_code(404);
        echo json_encode(['status' => 'error', 'message' => 'User not found']);
    }
} elseif ($method === 'POST' && $path === 'users') {
    $input = json_decode(file_get_contents('php://input'), true);
    // In a real app this would write to the database
    echo json_encode(['status' => 'ok', 'message' => 'User created']);
} else {
    http_response_code(404);
    echo json_encode(['status' => 'error', 'message' => 'Unknown endpoint']);
}
?>

▶ 試してみよう

3. Sending Email

(1) mail() Basics

PHP

<?php
$to = "user@example.com";
$subject = "=?UTF-8?B?" . base64_encode("Password Reset Notification") . "?="; // Encoded subject
$message = "Hello, please click the link below to reset your password:\n\n";
$message .= "https://myblog.com/reset?token=abc123";
$headers = "From: noreply@myblog.com\r\n";
$headers .= "Content-Type: text/plain; charset=UTF-8\r\n";

if (mail($to, $subject, $message, $headers)) {
    echo "Email sent ✅";
} else {
    echo "Email failed ❌";
}
?>

💡 Tip: mail() requires the server to have sendmail/Postfix configured. XAMPP doesn't include one by default—for testing email functionality, it's better to use SMTP (next section).

▶ サンプル: HTML Verification Email

PHP

<?php
function sendVerificationEmail(string $to, string $token): bool {
    $subject = "=?UTF-8?B?" . base64_encode("Please verify your email") . "?=";
    
    // HTML email
    $message = "<html><body>";
    $message .= "<h2>Welcome to MyBlog!</h2>";
    $message .= "<p>Please click the link below to verify your email:</p>";
    $message .= "<a href='https://myblog.com/verify?token={$token}'>Verify Email</a>";
    $message .= "<p>If the link doesn't work, copy and paste this address:</p>";
    $message .= "<p>https://myblog.com/verify?token={$token}</p>";
    $message .= "</body></html>";
    
    $headers = "From: noreply@myblog.com\r\n";
    $headers .= "MIME-Version: 1.0\r\n";
    $headers .= "Content-Type: text/html; charset=UTF-8\r\n";
    
    return mail($to, $subject, $message, $headers);
}

$token = bin2hex(random_bytes(32));
sendVerificationEmail('user@example.com', $token);
?>

▶ 試してみよう

4. PHPMailer (Recommended)

mail() is simple but limited. PHPMailer is the de facto standard for PHP email:

BASH

# Install
composer require phpmailer/phpmailer

PHP

<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require 'vendor/autoload.php';

function sendEmailSMTP(string $to, string $subject, string $body): bool {
    $mail = new PHPMailer(true);
    
    try {
        // Server settings
        $mail->isSMTP();
        $mail->Host       = 'smtp.gmail.com';    // SMTP server
        $mail->SMTPAuth   = true;
        $mail->Username   = 'your@gmail.com';     // Sender email
        $mail->Password   = 'app-password';       // App-specific password
        $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
        $mail->Port       = 587;
        $mail->CharSet    = 'UTF-8';
        
        // Recipients
        $mail->setFrom('your@gmail.com', 'MyBlog');
        $mail->addAddress($to);
        
        // Content
        $mail->isHTML(true);
        $mail->Subject = $subject;
        $mail->Body    = $body;
        $mail->AltBody = strip_tags($body);  // Plain-text fallback
        
        $mail->send();
        return true;
    } catch (Exception $e) {
        echo "Email failed: {$mail->ErrorInfo}";
        return false;
    }
}

sendEmailSMTP(
    'user@example.com',
    'Password Reset',
    '<h3>MyBlog Password Reset</h3><p>Click <a href="#">here</a> to reset your password.</p>'
);
?>

💡 Tip: When testing with Gmail: enable 2-step verification → generate an app-specific password → use that password (not your Gmail login password). Gmail will reject connections if you use your actual password directly.

5. Email Best Practices

PHP

<?php
class MailService {
    public function sendWelcome(string $email, string $username): bool {
        $subject = "Welcome to MyBlog";
        $body = file_get_contents(__DIR__ . '/templates/welcome.html');
        $body = str_replace('{{username}}', htmlspecialchars($username), $body);
        
        return sendEmailSMTP($email, $subject, $body);
    }
    
    public function sendPasswordReset(string $email, string $token): bool {
        $link = "https://myblog.com/reset?token={$token}";
        $subject = "Password Reset";
        $body = "
            <h3>Password Reset Request</h3>
            <p>Click the link below to reset your password (valid for 1 hour):</p>
            <a href='{$link}'>{$link}</a>
            <p>If you didn't request a password reset, please ignore this email.</p>
        ";
        return sendEmailSMTP($email, $subject, $body);
    }
    
    public function sendNotification(string $email, string $title, string $message): bool {
        $subject = "📢 {$title}";
        $body = "<h3>{$title}</h3><p>{$message}</p>";
        return sendEmailSMTP($email, $subject, $body);
    }
}
?>

❓ よくある質問

Q Why is JSON more popular than XML?

A It's lightweight (fewer tags), natively supported by JavaScript (JSON.parse), and highly readable. In PHP, json_encode/json_decode handles it in one line, whereas XML takes several steps.

Q Should I use mail() or an SMTP library?

A mail() is convenient for local dev (if configured). Use an SMTP library (PHPMailer) in production—it has better error handling, supports attachments, multiple recipients, and isn't affected by server mail configuration.

Q Can I use a JSON file as a database?

A Yes, for small datasets and single-user scenarios (like config files). For multi-user concurrent reads/writes and complex queries, you must use MySQL. The problems with JSON as a database: no concurrent writes, no indexes so slow queries, and performance degrades as data grows.

📖 まとめ

json_encode($data, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT) serializes data
json_decode($json, true) parses JSON (true=array, default=object)
json_last_error_msg() checks for parse errors
mail() is simple but requires server configuration; encoded subjects use base64_encode
In production, use SMTP (PHPMailer)—it supports attachments, HTML, and encryption
JSON files suit single-user configs and API transfers; multi-user data belongs in a database

📝 練習問題

Create a settings.json config file and use PHP to read and display all configuration items.
Write a simple JSON API: /users returns all users, /users/1 returns the user with ID=1. Simulate with GET parameters.
Add email verification to your registration system: generate a verification token on registration (store in a file/database), send a verification email (test locally with mail() or SMTP).

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