Most efficient way to check a URL - php

Question

I'm trying to check if a user submitted URL is valid, it goes directly to the database when the user hits submit.
So far, I have:
$string = $_POST[url];
if (strpos($string, 'www.') && (strpos($string, '/')))
{
echo 'Good';
}
The submitted page should be a page in a directory, not the main site, so http://www.address.com/page
How can I have it check for the second / without it thinking it's from http:// and that doesn't include .com?
Sample input:
Valid:
http://www.facebook.com/pageName
http://www.facebook.com/pageName/page.html
http://www.facebook.com/pageName/page.*
Invalid:
http://www.facebook.com
facebook.com/pageName
facebook.com

Answer 1

if(!parse_url('http://www.address.com/page', PHP_URL_PATH)) {
echo 'no path found';
}
See parse_url reference.

Answer 2

See the parse_url() function. This will give you the "/page" part of the URL in a separate string, which you can then analyze as desired.

Answer 3

filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED)
More information here :
http://ca.php.net/filter_var

Answer 4

Maybe strrpos will help you. It will locate the last occurrence of a string within a string

Answer 5

To check the format of the URL you could use a regular expression:
preg_match [ http://php.net/manual/en/function.preg-match.php ] is a good start, but a knowledge of regular expressions is needed to make it work.
Additionally, if you actually want to check that it's a valid URL, you could check the URL value to see if it actually resolves to a web page:
function check_404($url) {
$return = #get_headers($url);
if (strpos($return[0], ' 404 ') === false)
return true;
else {
return false;
}
}

Answer 6

Try using a regular expression to see that the URL has the correct structure. Here's more reading on this. You need to learn how PCRE works.
A simple example for what you want (disclaimer: not tested, incomplete).
function isValidUrl($url) {
return preg_match('#http://[^/]+/.+#', $url));
}

Answer 7

From here: http://www.blog.highub.com/regular-expression/php-regex-regular-expression/php-regex-validating-a-url/
<?php
/**
* Validate URL
* Allows for port, path and query string validations
* #param string $url string containing url user input
* #return boolean Returns TRUE/FALSE
*/
function validateURL($url)
{
$pattern = '/^(([\w]+:)?\/\/)?(([\d\w]|%[a-fA-f\d]{2,2})+(:([\d\w]|%[a-fA-f\d]{2,2})+)?#)?([\d\w][-\d\w]{0,253}[\d\w]\.)+[\w]{2,4}(:[\d]+)?(\/([-+_~.\d\w]|%[a-fA-f\d]{2,2})*)*(\?(&?([-+_~.\d\w]|%[a-fA-f\d]{2,2})=?)*)?(#([-+_~.\d\w]|%[a-fA-f\d]{2,2})*)?$/';
return preg_match($pattern, $url);
}
$result = validateURL('http://www.google.com');
print $result;
?>