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";

在FILTER_VALIDATE_EMAIL中有一个更好的正则表达式，但任何正则表达式都可能给出糟糕的结果。

例如. .

// "not an email" is invalid so its false.
php > var_export(filter_var("not an email", FILTER_VALIDATE_EMAIL));
false
// "foo@a.com" looks like an email, so it passes even though its not real.
php > var_export(filter_var("foo@a.com", FILTER_VALIDATE_EMAIL));
'foo@a.com'
// "foo@gmail.com" passes, gmail is a valid email server,
//  but gmail require more than 3 letters for the address.
var_export(filter_var("foo@gmail.com", FILTER_VALIDATE_EMAIL));
'foo@gmail.com'

你可能会考虑使用像Real Email这样的API，它可以进行深入的邮箱检查，以检查电子邮件是否真实。

有点像…

$email = "foo@bar.com";
$api_key = ???;

$request_context = stream_context_create(array(
    'http' => array(
        'header'  => "Authorization: Bearer " . $api_key
    )
));

$result_json = file_get_contents("https://isitarealemail.com/api/email/validate?email=" . $email, false, $request_context);

if (json_decode($result_json, true)['status'] == "valid") {
    echo("email is valid");
} else if (json_decode($result_json, true)['status'] == "invalid") {
    echo("email is invalid");
} else {
  echo("email was unknown");
}

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;
}

您可以为此使用filter_var。

<?php
   function validateEmail($email) {
      return filter_var($email, FILTER_VALIDATE_EMAIL);
   }
?>

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。

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;
}