从URL中读取网页内容

I am making a website in which the user will provide with URL of some other page and the code will read (not open) it and extract a part of the page.

Say, I provide URL for this page, and I get the question header of the page.

How can I do that.?

I tried using AJAX, creating object of HTTPRequest, but was not able to read a particular part of the page. (say innerHTML of some #id)

there is a php lib made for this and its called PHP Simple HTML DOM Parser

// Create DOM from URL or file
$html = file_get_html('http://www.google.com/');

// Find all images 
foreach($html->find('img') as $element) 
       echo $element->src . '<br>';

// Find all links 
foreach($html->find('a') as $element) 
       echo $element->href . '<br>';

Syntax:

file_get_contents("URL");

Example:

echo file_get_contents('http://www.stackoverflow.com');