Passing Colon in curl function issue - php

Question

I have this function:
function file_get_contents_curl($url) {
$ch = curl_init();
$ua = 'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)';
curl_setopt($ch, CURLOPT_AUTOREFERER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);
curl_setopt($ch, CURLOPT_USERAGENT, $ua);
$data = curl_exec($ch);
curl_close($ch);
return $data;
}
Now I have a strange issue: I;m trying to search in Google
using the "inurl:example.com", like this:
$email = $_GET["email"];
$in = "inurl:example.com+" . $email;
$in = str_replace(' ','+',$in);
$url = 'http://www.google.com/search?hl=en&q='.$in;
and every time i get 0 results.
However, when i get rid from the "inurl:" and replace it with some other
condition, like this:
$in = "example.com+" . $email;
it works well and i see the results.
So something about the COLON ("inurl:") causes trouble for the file_get_contents_curl function.
I tried the same inurl: string in file_get_html function (instead of file_get_contents_curl)
$html = file_get_html($url);
with no problem at all.
Any ideas?
EDIT:
$in = "+inurl:pastebin.com";
$in = str_replace("%3A",":",$in);
(NOT) solved the problem.
EDIT:
Sometimes it works and sometimes not.
So it's something related to Google blocking/rate-limit
and stuff like that.
Thanks anyway.