How does PHP Verify that the URL is correct?

How does PHP Verify that the URL is correct??
The URL format is:
Http://www.abc.com
http://ABC.com
http://www.abc.com/
http://ABC.com
http://www.abc.com/s/

http://www.abc.com/s/s/

Http://www.abc.com/s/xx.htm

http://www.abc.com/s/xx.php

http://www.abc.com/s/xx.asp/

Https://www.abc.com/s/xx

ftp://www.abc.com/

Wait a minute

if (Preg_match ("/????????????????? ", $url)) {//How to write here? Able to deal with various possible URL formats?
echo "URL is correct";
}else{
echo "URL error";
}




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Contains com|cn|net front dot, followed by/or empty to determine the URL
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discuss

I know how to use the regular, the key is how to write, but also to take into account all the above-mentioned format

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Then refer to this article Http://www.pin 5i.com/showtopic-25932.html

It's not PHP, but it should be about the same.

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What's wrong with CSDN?!

Posted on the URL is not allowed to send, prompted that "your reply body has illegal words or phrases!" ”。

I had to insert a space in the middle. What the hell is this? What's wrong with that website?



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