如果你只是在寻找一个实际的正则表达式，允许各种点，下划线和破折号，它如下:[a-zA-z0-9.-]+\@[a-zA-z0-9.-]+.[a-zA-Z]+。这将允许像tom_anderson.1-neo@my-mail_matrix.com这样看起来相当愚蠢的电子邮件被验证。

我准备了一个检查电子邮件有效性的函数:

function isValidEmail($email)
{
    $re = '/([\w\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)/m';
    preg_match_all($re, $email, $matches, PREG_SET_ORDER, 0);
    if(count($matches) > 0) return $matches[0][0] === $email;
    return false;
}

FILTER_VALIDATE_EMAIL的问题是，它甚至认为无效的电子邮件是有效的。

以下是例子:

if(isValidEmail("foo@gmail.com")) echo "valid";
if(!isValidEmail("fo^o@gmail.com")) echo "invalid";

如果你只是在寻找一个实际的正则表达式，允许各种点，下划线和破折号，它如下:[a-zA-z0-9.-]+\@[a-zA-z0-9.-]+.[a-zA-Z]+。这将允许像tom_anderson.1-neo@my-mail_matrix.com这样看起来相当愚蠢的电子邮件被验证。

看完这里的答案后，我得出了以下结论:

public static function isValidEmail(string $email) : bool
{
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        return false;
    }

    //Get host name from email and check if it is valid
    $email_host = array_slice(explode("@", $email), -1)[0];

    // Check if valid IP (v4 or v6). If it is we can't do a DNS lookup
    if (!filter_var($email_host,FILTER_VALIDATE_IP, [
        'flags' => FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE,
    ])) {
        //Add a dot to the end of the host name to make a fully qualified domain name
        // and get last array element because an escaped @ is allowed in the local part (RFC 5322)
        // Then convert to ascii (http://us.php.net/manual/en/function.idn-to-ascii.php)
        $email_host = idn_to_ascii($email_host.'.');

        //Check for MX pointers in DNS (if there are no MX pointers the domain cannot receive emails)
        if (!checkdnsrr($email_host, "MX")) {
            return false;
        }
    }

    return true;
}

在关于电子邮件验证的“顶级问题”中回答了这个问题https://stackoverflow.com/a/41129750/1848217

For me the right way for checking emails is: Check that symbol @ exists, and before and after it there are some non-@ symbols: /^[^@]+@[^@]+$/ Try to send an email to this address with some "activation code". When the user "activated" his email address, we will see that all is right. Of course, you can show some warning or tooltip in front-end when user typed "strange" email to help him to avoid common mistakes, like no dot in domain part or spaces in name without quoting and so on. But you must accept the address "hello@world" if user really want it. Also, you must remember that email address standard was and can evolute, so you can't just type some "standard-valid" regexp once and for all times. And you must remember that some concrete internet servers can fail some details of common standard and in fact work with own "modified standard".

所以，只要检查@，提示用户在前端和发送验证电子邮件在给定的地址。

根据我的经验，regex解决方案有太多的假阳性，而filter_var()解决方案有假阴性(特别是对于所有新的tld)。

相反，最好是确保地址具有电子邮件地址的所有必需部分(用户、“@”符号和域)，然后验证域本身是否存在。

无法确定(服务器端)外部域是否存在电子邮件用户。

这是我在Utility类中创建的一个方法:

public static function validateEmail(string $email): bool {

    // SET INITIAL RETURN VARIABLE
    // ENSURE -> EMAIL ISN'T EMPTY | AN @ SYMBOL IS PRESENT 

        $emailIsValid = FALSE;

        if (
            !empty($email) &&
            strpos($email, '@') !== FALSE
        ) {

            // GET EMAIL PARTS

                $email  = explode('@', $email);
                $user   = $email[0];
                $domain = $email[1];

            // VALIDATE EMAIL ADDRESS

                if (
                    count($email) === 2 &&
                    !empty($user) &&
                    !empty($domain) &&
                    checkdnsrr($domain)
                ) {
                    $emailIsValid = TRUE;
                }
        }

    // RETURN RESULT

        return $emailIsValid;
}