Strange toruble with sibple regexp

[KJedi]

I have a trouble: my code doesn't work. Here is it:

 $string = 'http://www.site.ru';
 $pattern = '!http//(.*?)!';
 $replacement = "<a href=\"http://\\1\">http://\\1</a>";
 echo preg_replace($pattern, $replacement, $string); 

It outputs only http://www.site.ru!

[Mav3n]

What do you want it to output?

[KJedi]

Oh, I wrote http// instead of http://

[KJedi]

What do you want it to output?

highlighted url

[KJedi]

I changed it to this:

 $string = 'http://www.site.ru';
 $pattern = '!http://(.*?)!is';
 $replacement = "<a href=\"http://\\1\">http://\\1</a>";
 echo preg_replace($pattern, $replacement, $string); 

But it highlights only http://:
http://www.site.ru
Why?

[KJedi]

Correct is:

 $string = 'http://www.site.ru';
 $pattern = '!http://(.*)!is';
 $replacement = "<a href=\"http://\\1\">http://\\1</a>";
 echo preg_replace($pattern, $replacement, $string);