What to do if PHP mailbox validity verification fails

Recently, when developing a website, I encountered some problems related to email validity verification. Specifically, we hope to verify the validity of the email address when the user registers or logs in to ensure that the user enters the correct email address. However, after trying multiple methods, we found that there were some issues, especially when using PHP for validation, we encountered some errors that were difficult to resolve. In this article, I will share the issues we encountered and the solutions so that others can avoid these issues and be able to successfully implement email validation.

First, let’s review common email validity verification methods. Generally speaking, the most common method is to use JavaScript for validation, which can be implemented while the user enters information without reloading the web page. During this process, the input string can be checked to see if it conforms to the email format. If it matches, the verification result is displayed on the user interface.

However, JavaScript verification does not completely guarantee the validity of the email address. Specifically, some malicious users may use simple techniques to bypass this verification. For example, they could insert an invalid email address directly into the database, and JavaScript validation would not check for this.

In order to solve this problem, we need to verify the email validity on the server side. Typically, we would use a PHP script to achieve this. Specifically, we need to check whether the email address entered by the user matches certain rules. These rules are generally defined through regular expressions, for example:

function validate_email($email) {
  $regex = "/^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}$/i";
  return preg_match($regex, $email);
}

In this function, we use a regular expression that matches email addresses. This expression checks whether the input string conforms to some basic rules, such as it must contain the "@" symbol and the "." symbol, and no spaces or other special characters are allowed.

However, even if we use this approach, we may still encounter some problems. Specifically, we found in practice that some PHP mail servers have errors when processing email addresses. In this case, we will encounter the following error:

Warning: ereg() [function.ereg]: REG_BADRPT

The reason for this error is that the email address we use does not meet the format requirements of the server. The solution to this problem is to use more complex regular expressions to ensure that our email addresses comply with all possible format requirements. For example, we can use the following regular expression:

function validate_email($email) {
  $regex = "/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/";
  return preg_match($regex, $email);
}

This regular expression can match more possible email formats, including email addresses starting with numbers, letters, dashes, and periods.

However, even if we use more complex regular expressions, we may still encounter other problems. Sometimes, we will encounter errors similar to the following:

Deprecated: Function eregi() is deprecated in ... on line ...

The reason for this error is that the PHP version we are using no longer supports the eregi function. We need to replace the function with preg_match, for example:

if (preg_match("/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/", $_POST['email'])) {
  // 验证成功
} else {
  // 验证失败
  echo "Invalid email address";
}

Using the preg_match function can solve this problem.

To summarize, email address validity verification is a very important part of website development. To ensure the success of this process, we need to use a variety of different methods for verification, and we need to ensure that the methods we use meet the requirements of the current system. By understanding the errors we encountered and the solutions we adopted, we believe others can successfully implement email validation as well.

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