PHP REGEX to Validate Domain Name

[Xmen]

I would like to validate that a URL is valid. It does not have to be iron-clad but it should restrict big faults.

For example.. These should validate:

example.com
domain.extension
www.webaddress.ab.cd.ef
my-domain.name
domain123.name

This should not validate:
email@example.com
web address com
my_domain.name
example.123

How can this be performed withing the PHP programming environment ?

[Praetor]

If you are developing yourself in web programming environment then you need to look for every chnages that are getting committed every day and every moments. Some new chnages and terms are being applied every time.

But some of the rules never change, in order to this discussion :What about trying to have your script connect to the domain with fopen() if in case, it returns an error then it's mostly switched in the invalid zone. These are some of the rules that is needed to consider in such situation..

[Katty]

Validating an URL is a job that appears so frequent. You may have a form where visitors (users) have to enter a valid URL. You might desired to check that a referrer that you will echo on a page is valid to restrict injection of wrong code and linking to faulty sites.

While PHP facilitates with the parse_url function to parse a URL and return its components it still lacks some activities that will come in handy when validating a URL.

Properties that my is_url function gives:

1. Lets you mention which components are needed
2. Reports which components are missing
3. Cleans up the parts to comply with RFC2396 and return them as an array
4. Returns true if entire needed components are present

[kelfro]

For the impatient between you here´s a whole example first. It checks whether the HTTP_REFERER is valid and converts it into an truly URI before using it on our page.

$cleaned = array(); 
$error = 0; 
if (is_url($_SERVER['HTTP_REFERER'], PATH, $error, $cleaned)) { 
 if ($error & (SCHEME + AUTHORITY)) { 
  $_SERVER['HTTP_REFERER'] = make_abs($_SERVER['HTTP_REFERER'], 
$_SERVER['SCRIPT_URI']); 
 } elseif ($cleaned['authority']!= $_SERVER['SERVER_NAME']) { 
  echo "Referer is from other domain. We do not include it."; 
 } else { 
  $_SERVER['HTTP_REFERER'] = make_uri($cleaned); 
  echo "<br>$_SERVER[HTTP_REFERER]"; 
 } 
} else { 
 echo "errors: $error<br>"; 
}

[Zecho]

I am going to show you a script which validates the format of a URL text string. It might be used to test the URL submitted from a form. The format of the URL is assumed to be of the form: domain-name.co.in for example. There are mainly two scripts. One would be used to validate a URL and the other one perform the domain name validation. They make use of regular expression pattern matching.

<?php

$url = 'teSTgjhgj.co.in';
if (preg_match ("/^[a-z0-9][a-z0-9\-]+[a-z0-9](\.[a-z]{2,4})+$/i", $url)) {
print "$url url OK.";
} else {
print "$url url invalid!";
}
?>

<?php
// For domain validation
$domain = 'teSTgjhgj';
if (preg_match ("/^[a-z0-9][a-z0-9\-]+[a-z0-9]$/i", $domain)) {
print "$domain Domain OK.";
} else {
print "$domain Domain invalid!";
}
?>

[opaper]

Hey buddy, you also can use this to do what you need to perform and I will suggest you this function to validating URL.

      function checkLink ($url)
      {
          if(!@fopen($url, "r"))
             return false;
          else
             return true;  
      }
       
     
      checkLink("http://php.net");
      //returns true

[MindSpace]

I don't think, the validation is very easy task and can be done by every common visitor. This is done by the use having proper privilege to edit and manage all this.A domain possible to be validated properly through the DNS-lookups and not through a fopen($domain). You function will fail for some domains that are valid but are not prefixed with www . Please consider about my words ...

Thanks you so much ...