web crawler PHP

Hello,
I am supposed to construct a page that searches in specific websites to extract information, like those sites from where you can rent a car for example. There is a form in the site where the user selects some fields (for instance departure and drop-off date), then the data are submitted to the other page that searches 2-3 sites and finds which cars are available on those dates.
I wanted to ask if there are ready scripts to do that, if not, some hints on how to start.
I am familiar with PHP forms and data extraction from mysql databases, but when you extract data from other sites, I have no clue how I can begin and deal with it...

 

Well I'm not going to do your homework for you, but I can give you a few functions that might help.

php.net/curl

Or (if no post data is required)

php.net/file_get_contents

And
php.net/preg_match
php.net/preg_match_all


I guess these are the most important.

(Sorry for the not clickable links, I'm not yet allowed to post some)

 

Clickable:

www.php.net/curl
php.net/file_get_contents
php.net/preg_match
php.net/preg_match_all

As nico_swd says, they should be all you need. I'll also include this function, you'll need it during development.

I also find strip_tags useful for data extraction.

 

I like to use this:

function gofetch() {
$fp = @fsockopen("www.website.com", 80, $errno, $errstr, 30);
if (!$fp) {
   echo "$errstr ($errno)<br />\n";
} else {
   $out = "GET /anythingyouwant.html HTTP/1.1\r\n";

   $out .= "Host: www.website.com\r\n";
   $out .= "Connection: Close\r\n\r\n";

   fwrite($fp, $out);
   while (!feof($fp)) {
$d = fgets($fp);

     if (preg_match("/searching for/i", $d)) {
echo "I found it :" . $d;
}
}
}
}

PHP: