Tips for controlling the number of emails using PHP

With the development and popularization of the Internet, email, as an efficient, convenient and economical way of communication, is becoming more and more popular and widely used. However, the number of emails sent has become a problem. For the sender, excessive sending of emails will not only affect the normal work and life of the recipient, but also affect the recipient's impression and evaluation of the sender. Especially for operators, service providers and other enterprises, sending a large number of emails will not only cause congestion in the email system, but also affect the performance and stability of the email server. In severe cases, it may trigger spam filtering policies and cause email Misidentified as spam.

Therefore, when implementing the email sending function, it is very necessary and important to control the number of emails. As a popular programming language, PHP has a wealth of tools and technologies that can easily control the number of emails. Here are several techniques for controlling the number of emails.

1. SMTP server-based restrictions

When using an SMTP server to send emails, the SMTP server usually has certain restrictions, such as the maximum number of emails that can be sent per hour or per day. Therefore, we can control the number of emails sent according to the limits of the SMTP server. The specific implementation is as follows:

//连接SMTP服务器
$mail = new PHPMailer(true);
$mail->SMTPDebug = 0;
$mail->isSMTP();
$mail->Host = 'smtp.example.com';
$mail->SMTPAuth = true;
$mail->Username = 'username';
$mail->Password = 'password';
$mail->SMTPSecure = 'ssl';
$mail->Port = 465;

//添加收件人、主题、正文等信息

//发送邮件
if ($mail->send()) {
  echo '邮件发送成功';
} else {
  echo '邮件发送失败';
}

//获取SMTP服务器的发送限制
$limit = $mail->getSMTPInstance()->getSendLimit();
if ($limit) {
  echo 'SMTP服务器每小时最多可以发送'.$limit.'封邮件';
}

In the above code, we connect to the SMTP server through the PHPMailer class, and set the relevant information of the SMTP server, then add the recipient, subject, body and other information, and finally call send() method sends email. If the email is sent successfully, "Email sent successfully" is output, otherwise "Email sent failed" is output.

Next, we obtain the instance object of the SMTP server through the getSMTPInstance() method, and then call the getSendLimit() method to obtain the maximum number of emails that the SMTP server can send per hour. . If the return value is 0, it means there is no limit, otherwise the specific sending limit is returned.

2. Control based on mail queue

Mail queue is a common technology that achieves this by temporarily storing emails to be sent in the queue and then sending them one by one according to specific rules. The purpose of controlling the number and speed of sending emails. The specific implementation is as follows:

//将待发送的邮件添加到队列中
function addToQueue($to, $subject, $message) {
  $queueFile = 'mail_queue.txt';
  $data = serialize(array('to'=>$to, 'subject'=>$subject, 'message'=>$message));
  file_put_contents($queueFile, $data."
", FILE_APPEND | LOCK_EX);
}

//按照队列中的顺序发送邮件
function processQueue() {
  $queueFile = 'mail_queue.txt';
  if (!file_exists($queueFile) || !is_readable($queueFile)) {
    return false;
  }
  $f = fopen($queueFile, 'r');
  while ($data = fgets($f)) {
    $mail = unserialize(trim($data));
    $to = $mail['to'];
    $subject = $mail['subject'];
    $message = $mail['message'];
    //发送邮件
    //...
  }
  fclose($f);
  //清空队列
  file_put_contents($queueFile, '');
  return true;
}

In the above code, we define two functions: addToQueue() and processQueue(). addToQueue()The function is used to add a message to be sent to the queue, which contains information such as the recipient, subject, and body of the message. processQueue()The function is used to take out emails from the queue and send them one by one in the order of the queue.

In specific implementation, we can serialize the email information to be sent, store it in a text file, and then call the processQueue() function regularly in the background, one by one in the order of the queue. Read email information and perform email sending operations. This method can avoid the problem of mail system crash caused by sudden large amount of mail sending, and can also realize batch processing and control of mail sending.

3. Database-based restrictions

The database is also a common way to implement email sending control. We can set relevant parameters in the database, such as the maximum number of emails that can be sent per hour or per day, and then query and determine whether the sending limit has been exceeded when the email is sent. The specific implementation is as follows:

//连接数据库
$conn = new mysqli('localhost', 'username', 'password', 'database');
if ($conn->connect_error) {
  die('数据库连接失败：'.$conn->connect_error);
}

//查询发送数量
$count = $conn->query("SELECT COUNT(*) as total FROM emails WHERE sent_date >= DATE_SUB(NOW(), INTERVAL 1 HOUR)");
if (!$count) {
  die('查询失败：'.$conn->error);
}
$row = $count->fetch_assoc();
$total = $row['total'];

//判断发送限制
if ($total >= 100) {
  die('发送数量已达限制');
}

//插入邮件信息
$stmt = $conn->prepare("INSERT INTO emails (recipient, subject, content, sent_date) VALUES (?, ?, ?, NOW())");
$stmt->bind_param('sss', $to, $subject, $content);
if (!$stmt->execute()) {
  die('邮件发送失败：'.$conn->error);
} else {
  echo '邮件已添加到队列';
}
$stmt->close();
$conn->close();

In the above code, we connect to the database through mysqli, query the number of emails sent in the database in the last hour, and then determine whether the sending limit has been exceeded. If the limit is exceeded, the mail sending is stopped, otherwise the mail information is inserted into the database and waits for the background program to process.

It should be noted that when using a database to control the number of emails sent, we need to install and configure appropriate database software and set relevant parameters. In addition, a series of complex operations such as database connection, query, insertion and closing are required, making code writing more troublesome.

In summary, controlling the number of emails sent is very necessary in practical applications to avoid congestion and collapse of the email system and ensure the normal operation of the email system. In PHP, the techniques for controlling the number of emails mainly include SMTP server-based restrictions, mail queue-based controls, and database-based restrictions. When choosing a specific implementation method, it is necessary to comprehensively consider and evaluate the specific situation and needs to select the optimal solution.

The above is the detailed content of Tips for controlling the number of emails using PHP. For more information, please follow other related articles on the PHP Chinese website!