问题
Is it possible without using regular expression?
For example, I want to check that a string is a valid domain:
domain-name
abcd
example
Are valid domains. These are invalid of course:
domaia@name
ab$%cd
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.
If it\'s not possible, could you suggest me a regexp pattern to do this?
EDIT:
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, $domain)) {
throw new Exception(\'Domain invalid\');
}
回答1:
<?php
function is_valid_domain_name($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
}
?>
Test cases:
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
回答2:
With this you will not only be checking if the domain has a valid format, but also if it is active / has an IP address assigned to it.
$domain = "stackoverflow.com";
if(filter_var(gethostbyname($domain), FILTER_VALIDATE_IP))
{
return TRUE;
}
Note that this method requires the DNS entries to be active so if you require a domain string to be validated without being in the DNS use the regular expression method given by velcrow above.
Also this function is not intended to validate a URL string use FILTER_VALIDATE_URL for that. We do not use FILTER_VALIDATE_URL for a domain because a domain string is not a valid URL.
回答3:
PHP 7
// Validate a domain name
var_dump(filter_var('mandrill._domainkey.mailchimp.com', FILTER_VALIDATE_DOMAIN));
# string(33) "mandrill._domainkey.mailchimp.com"
// Validate an hostname (here, the underscore is invalid)
var_dump(filter_var('mandrill._domainkey.mailchimp.com', FILTER_VALIDATE_DOMAIN, FILTER_FLAG_HOSTNAME));
# bool(false)
It is not documented here: http://www.php.net/filter.filters.validate and a bug request for this is located here: https://bugs.php.net/bug.php?id=72013
回答4:
Firstly, you should clarify whether you mean:
- individual domain name labels
- entire domain names (i.e. multiple dot-separate labels)
- host names
The reason the distinction is necessary is that a label can technically include any characters, including the NUL, @ and '.' characters. DNS is 8-bit capable and it's perfectly possible to have a zone file containing an entry reading "an\0odd\.l@bel". It's not recommended of course, not least because people would have difficulty telling a dot inside a label from those separating labels, but it is legal.
However, URLs require a host name in them, and those are governed by RFCs 952 and 1123. Valid host names are a subset of domain names. Specifically only letters, digits and hyphen are allowed. Furthermore the first and last characters cannot be a hyphen. RFC 952 didn't permit a number for the first character, but RFC 1123 subsequently relaxed that.
Hence:
a- valid0- valida-- invalida-b- validxn--dasdkhfsd- valid (punycode encoding of an IDN)
Off the top of my head I don't think it's possible to invalidate the a- example with a single simple regexp. The best I can come up with to check a single host label is:
if (preg_match('/^[a-z\d][a-z\d-]{0,62}$/i', $label) &&
!preg_match('/-$/', $label))
{
# label is legal within a hostname
}
To further complicate matters, some domain name entries (typically SRV records) use labels prefixed with an underscore, e.g. _sip._udp.example.com. These are not host names, but are legal domain names.
回答5:
use checkdnsrr http://php.net/manual/en/function.checkdnsrr.php
$domain = "stackoverflow.com";
checkdnsrr($domain , "A");
//returns true if has a dns A record, false otherwise
回答6:
I think once you have isolated the domain name, say, using Erklan's idea:
$myUrl = "http://www.domain.com/link.php"; $myParsedURL = parse_url($myUrl); $myDomainName= $myParsedURL['host'];
you could use :
if( false === filter_var( $myDomainName, FILTER_VALIDATE_URL ) ) {
// failed test
}
PHP5s Filter functions are for just such a purpose I would have thought.
It does not strictly answer your question as it does not use Regex, I realise.
回答7:
Here is another way without regex.
$myUrl = "http://www.domain.com/link.php";
$myParsedURL = parse_url($myUrl);
$myDomainName= $myParsedURL['host'];
$ipAddress = gethostbyname($myDomainName);
if($ipAddress == $myDomainName)
{
echo "There is no url";
}
else
{
echo "url found";
}
回答8:
Regular expression is the most effective way of checking for a domain validation. If you're dead set on not using a Regular Expression (which IMO is stupid), then you could split each part of a domain:
- www. / sub-domain
- domain name
- .extension
You would then have to check each character in some sort of a loop to see that it matches a valid domain.
Like I said, it's much more effective to use a regular expression.
回答9:
Your regular expression is fine, but you're not using preg_match right. It returns an int (0 or 1), not a boolean. Just write if(!preg_match($regex, $string)) { ... }
回答10:
If you don't want to use regular expressions, you can try this:
$str = 'domain-name';
if (ctype_alnum(str_replace('-', '', $str)) && $str[0] != '-' && $str[strlen($str) - 1] != '-') {
echo "Valid domain\n";
} else {
echo "Invalid domain\n";
}
but as said regexp are the best tool for this.
回答11:
If you want to check whether a particular domain name or ip address exists or not, you can also use checkdnsrr
Here is the doc http://php.net/manual/en/function.checkdnsrr.php
回答12:
A valid domain is for me something I'm able to register or at least something that looks like I could register it. This is the reason why I like to separate this from "localhost"-names.
And finally I was interested in the main question if avoiding Regex would be faster and this is my result:
<?php
function filter_hostname($name, $domain_only=false) {
// entire hostname has a maximum of 253 ASCII characters
if (!($len = strlen($name)) || $len > 253
// .example.org and localhost- are not allowed
|| $name[0] == '.' || $name[0] == '-' || $name[ $len - 1 ] == '.' || $name[ $len - 1 ] == '-'
// a.de is the shortest possible domain name and needs one dot
|| ($domain_only && ($len < 4 || strpos($name, '.') === false))
// several combinations are not allowed
|| strpos($name, '..') !== false
|| strpos($name, '.-') !== false
|| strpos($name, '-.') !== false
// only letters, numbers, dot and hypen are allowed
/*
// a little bit slower
|| !ctype_alnum(str_replace(array('-', '.'), '', $name))
*/
|| preg_match('/[^a-z\d.-]/i', $name)
) {
return false;
}
// each label may contain up to 63 characters
$offset = 0;
while (($pos = strpos($name, '.', $offset)) !== false) {
if ($pos - $offset > 63) {
return false;
}
$offset = $pos + 1;
}
return $name;
}
?>
Benchmark results compared with velcrow 's function and 10000 iterations (complete results contains many code variants. It was interesting to find the fastest.):
filter_hostname($domain);// $domains: 0.43556308746338 $real_world: 0.33749794960022
is_valid_domain_name($domain);// $domains: 0.81832790374756 $real_world: 0.32248711585999
$real_world did not contain extreme long domain names to produce better results. And now I can answer your question: With the usage of ctype_alnum() it would be possible to realize it without regex, but as preg_match() was faster I would prefer that.
If you don't like the fact that "local.host" is a valid domain name use this function instead that valids against a public tld list. Maybe someone finds the time to combine both.
回答13:
The correct answer is that you don't ... you let a unit tested tool do the work for you:
// return '' if host invalid --
private function setHostname($host = '')
{
$ret = (!empty($host)) ? $host : '';
if(filter_var('http://'.$ret.'/', FILTER_VALIDATE_URL) === false) {
$ret = '';
}
return $ret;
}
further reading :https://www.w3schools.com/php/filter_validate_url.asp
回答14:
I know that this is an old question, but it was the first answer on a Google search, so it seems relevant. I recently had this same problem. The solution in my case was to just use the Public Suffix List:
https://publicsuffix.org/learn/
The suggested language specific libraries listed should all allow for easy validation of not just domain format, but also top level domain validity.
回答15:
If you can run shell commands, following is the best way to determine if a domain is registered.
This function returns false, if domain name isn't registered else returns domain name.
function get_domain_name($domain) {
//Step 1 - Return false if any shell sensitive chars or space/tab were found
if(escapeshellcmd($domain)!=$domain || count(explode(".", $domain))<2 || preg_match("/[\s\t]/", $domain)) {
return false;
}
//Step 2 - Get the root domain in-case of subdomain
$domain = (count(explode(".", $domain))>2 ? strtolower(explode(".", $domain)[count(explode(".", $domain))-2].".".explode(".", $domain)[count(explode(".", $domain))-1]) : strtolower($domain));
//Step 3 - Run shell command 'dig' to get SOA servers for the domain extension
$ns = shell_exec(escapeshellcmd("dig +short SOA ".escapeshellarg(explode(".", $domain)[count(explode(".", $domain))-1])));
//Step 4 - Return false if invalid extension (returns NULL), or take the first server address out of output
if($ns===NULL) {
return false;
}
$ns = (((preg_split('/\s+/', $ns)[0])[strlen(preg_split('/\s+/', $ns)[0])-1]==".") ? substr(preg_split('/\s+/', $ns)[0], 0, strlen(preg_split('/\s+/', $ns)[0])-1) : preg_split('/\s+/', $ns)[0]);
//Step 5 - Run another dig using the obtained address for our domain, and return false if returned NULL else return the domain name. This assumes an authoritative NS is assigned when a domain is registered, can be improved to filter more accurately.
$ans = shell_exec(escapeshellcmd("dig +noall +authority ".escapeshellarg("@".$ns)." ".escapeshellarg($domain)));
return (($ans===NULL) ? false : ((strpos($ans, $ns)>-1) ? false : $domain));
}
Pros
- Works on any domain, while php dns functions may fail on some domains. (my .pro domain failed on php dns)
- Works on fresh domains without any dns (like A) records
- Unicode friendly
Cons
- Usage of shell execution, probably
回答16:
<?php
if(is_valid_domain('https://www.google.com')==1){
echo 'Valid';
}else{
echo 'InValid';
}
function is_valid_domain($url){
$validation = FALSE;
/*Parse URL*/
$urlparts = parse_url(filter_var($url, FILTER_SANITIZE_URL));
/*Check host exist else path assign to host*/
if(!isset($urlparts['host'])){
$urlparts['host'] = $urlparts['path'];
}
if($urlparts['host']!=''){
/*Add scheme if not found*/ if (!isset($urlparts['scheme'])){
$urlparts['scheme'] = 'http';
}
/*Validation*/
if(checkdnsrr($urlparts['host'], 'A') && in_array($urlparts['scheme'],array('http','https')) && ip2long($urlparts['host']) === FALSE){
$urlparts['host'] = preg_replace('/^www\./', '', $urlparts['host']);
$url = $urlparts['scheme'].'://'.$urlparts['host']. "/";
if (filter_var($url, FILTER_VALIDATE_URL) !== false && @get_headers($url)) {
$validation = TRUE;
}
}
}
return $validation;
}
?>
回答17:
Check the php function checkdnsrr
function validate_email($email){
$exp = "^[a-z\'0-9]+([._-][a-z\'0-9]+)*@([a-z0-9]+([._-][a-z0-9]+))+$";
if(eregi($exp,$email)){
if(checkdnsrr(array_pop(explode("@",$email)),"MX")){
return true;
}else{
return false;
}
}else{
return false;
}
}
回答18:
This is validation of domain name in javascript:
<script>
function frmValidate() {
var val=document.frmDomin.name.value;
if (/^[a-zA-Z0-9][a-zA-Z0-9-]{1,61}[a-zA-Z0-9](?:\.[a-zA-Z]{2,})+$/.test(val)){
alert("Valid Domain Name");
return true;
} else {
alert("Enter Valid Domain Name");
val.name.focus();
return false;
}
}
</script>
回答19:
This is simple. Some php egnine has a problem with split(). This code below will work.
<?php
$email = "vladimiroliva@ymail.com";
$domain = strtok($email, "@");
$domain = strtok("@");
if (@getmxrr($domain,$mxrecords))
echo "This ". $domain." EXIST!";
else
echo "This ". $domain." does not exist!";
?>
来源：https://stackoverflow.com/questions/1755144/how-to-validate-domain-name-in-php