如何在PHP中验证域名? [英] How to validate domain name in PHP?

问题描述

是否可以不使用正则表达式?

Is it possible without using regular expression?

例如，我要检查字符串是否为有效域:

For example, I want to check that a string is a valid domain:

domain-name
abcd
example

是有效域.这些当然是无效的:

Are valid domains. These are invalid of course:

domaia@name
ab$%cd

以此类推.因此，基本上应该以字母数字字符开头，然后可能会有更多的字母字符和连字符.并且还必须以字母数字结尾.

And so on. So basically it should start with an alphanumeric character, then there may be more alnum characters plus also a hyphen. And it must end with an alnum character, too.

如果不可能，您能建议我使用正则表达式模式吗?

If it's not possible, could you suggest me a regexp pattern to do this?

为什么这行不通?我使用的preg_match不正确吗?

Why doesn't this work? Am I using preg_match incorrectly?

$domain = '@djkal';
$regexp = '/^[a-zA-Z0-9][a-zA-Z0-9\-\_]+[a-zA-Z0-9]$/';
if (false === preg_match($regexp, $domain)) {
    throw new Exception('Domain invalid');
}

推荐答案

<?php
function is_valid_domain_name($domain_name)
{
    return (preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) //valid chars check
            && preg_match("/^.{1,253}$/", $domain_name) //overall length check
            && preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)   ); //length of each label
}
?>

测试用例:

is_valid_domain_name? [a]                       Y
is_valid_domain_name? [0]                       Y
is_valid_domain_name? [a.b]                     Y
is_valid_domain_name? [localhost]               Y
is_valid_domain_name? [google.com]              Y
is_valid_domain_name? [news.google.co.uk]       Y
is_valid_domain_name? [xn--fsqu00a.xn--0zwm56d] Y
is_valid_domain_name? [goo gle.com]             N
is_valid_domain_name? [google..com]             N
is_valid_domain_name? [google.com ]             N
is_valid_domain_name? [google-.com]             N
is_valid_domain_name? [.google.com]             N
is_valid_domain_name? [<script]                 N
is_valid_domain_name? [alert(]                  N
is_valid_domain_name? [.]                       N
is_valid_domain_name? [..]                      N
is_valid_domain_name? [ ]                       N
is_valid_domain_name? [-]                       N
is_valid_domain_name? []                        N

这篇关于如何在PHP中验证域名?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！