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");
}

使用以下代码:

// Variable to check
$email = "john.doe@example.com";

// Remove all illegal characters from email
$email = filter_var($email, FILTER_SANITIZE_EMAIL);


// Validate e-mail
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo("Email is a valid email address");
}

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。

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");
}

如果你想检查电子邮件地址提供的域名是否有效，可以使用如下方法:

/*
* Check for valid MX record for given email domain
*/
if(!function_exists('check_email_domain')){
    function check_email_domain($email) {
        //Get host name from email and check if it is valid
        $email_host = explode("@", $email);     
        //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)
        $host = end($email_host) . "."; 
        //Convert to ascii (http://us.php.net/manual/en/function.idn-to-ascii.php)
        return checkdnsrr(idn_to_ascii($host), "MX"); //(bool)       
    }
}

这是一种方便的方式来过滤大量无效的电子邮件地址，以及标准的电子邮件验证，因为有效的电子邮件格式并不意味着有效的电子邮件。

请注意，idn_to_ascii()(或它的姐妹函数idn_to_utf8())函数在PHP安装中可能不可用，它需要扩展PECL intl >= 1.0.2和PECL idn >= 0.1。

还要记住，IPv4或IPv6作为电子邮件中的域部分(例如user@[IPv6:2001:db8::1])不能被验证，只有命名主机可以。

点击这里查看更多信息。

检查电子邮件地址是否格式良好的最简单和最安全的方法是使用filter_var()函数:

if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // invalid emailaddress
}

此外，您可以检查域是否定义了MX记录:

if (!checkdnsrr($domain, 'MX')) {
    // domain is not valid
}

但这仍然不能保证邮件存在。唯一的办法就是发送确认邮件。

现在你已经有了简单的答案，如果你想学习，可以继续阅读关于电子邮件地址验证的内容，或者只是使用快速答案并继续前进。别见怪不怪。

尝试使用正则表达式验证电子邮件地址是一项“不可能”的任务。我想说的是，你所做的正则表达式是无用的。关于电子邮件地址有三个rfc，编写一个正则表达式来捕获错误的电子邮件地址，同时避免误报，这是没有人能做到的。查看PHP的filter_var()函数所使用的正则表达式的测试列表(包括失败和成功)。

即使是内置的PHP函数，电子邮件客户端或服务器也没有做到这一点。在大多数情况下，filter_var仍然是最好的选择。

如果你想知道PHP(目前)使用哪种正则表达式模式来验证电子邮件地址，请参阅PHP源代码。

如果你想了解更多关于电子邮件地址的信息，我建议你开始阅读说明书，但我必须警告你，无论如何，这都不是一个简单的阅读:

rfc5322 rfc5321 rfc3696 Rfc6531(允许unicode字符，尽管许多客户端/服务器不接受它)