<?php
/***********
* This script takes html retrieved from the remote server and changes all links
* so that it will lead to the script itself with original URL as parameter
*
*/
class ParseHtml{
var $tag_modifications = array ();//tags modifications
var $source_html; //page recieved from the web server
var $html = ""; //html to display to user agent
var $URI; //object with parsed url of html page
//array of correspondence
var $tag_attributes = array("A" => "HREF",
"LINK" => "HREF",
"IMG" => "SRC",
"FORM" => "ACTION"
);
function ParseHtml($html, $URI_obj){
global $HTTP_SERVER_VARS;
$this->source_html = $html;
$this->URI =& $URI_obj;
$this->script_url = "http://".$HTTP_SERVER_VARS['HTTP_HOST'].$HTTP_SERVER_VARS["SCRIPT_NAME"];
//offset - position of the parser
$offset = 0;
$done = false;
while (!$done){
//finding tag opening
$tag_open_pos = strpos ($html, "<", $offset);
if ($tag_open_pos === false){
//no more tags - just adding the rest of the contents
$this->html .= substr ($this->source_html, $offset);
break;
}
//there is a tag opening smbol, add preceding page contents
//(after prev. tag)
$this->html .= substr ($this->source_html, $offset, $tag_open_pos-$offset);
//moving the parse pointer to the beginning of the tag
$offset = $tag_open_pos+1;
//finding the position of ">" symbol
$tag_close_pos = strpos ($html, ">", $offset);
//if there is no closing ">", considering it's the last tag, process it
//and break the cycle
//else move parse pointer behind the end of the tag and continue
if ($tag_close_pos){
//get the content of the tag to analyse
$tag_content = trim (substr($html, $tag_open_pos+1, $tag_close_pos-$tag_open_pos-1));
//change the tag, if needed
if ($this->is_opening_tag("<$tag_content")){
$new_tag = $this->change_tag ($tag_content);
}else{
$new_tag = $tag_content;
}
//add tag (changed or not) to the page
$this->html .= "<". $new_tag . ">";
//move page pointer behind the end of the tag
$offset = $tag_close_pos+1;
}else{
$tag_content = trim (substr($html, $tag_open_pos+1));
if ($this->is_opening_tag("<$tag_content")){
$new_tag = $this->change_tag ($tag_content);
}else{
$new_tag = $tag_content;
}
$this->html .= "<". $new_tag . ">";
break;
}
unset ($tag_open_pos, $tag_close_pos);
}
}
function is_opening_tag($tag){
return !preg_match("~^< */~", $tag);
}
//change tag attribute's value
//making the changes in the tags
function change_tag ($tag_content){
//get tag name
$space_position = strpos($tag_content, " ");
if ($space_position){//tag has attributes
$tag_name = substr($tag_content, 0, $space_position);
}else return ($tag_content);
//should we change this tag?
if (!array_key_exists(strtoupper($tag_name), $this->tag_attributes)){
return ($tag_content);
}
$attr_name = $this->tag_attributes[strtoupper($tag_name)];
//get the value of the attribute
//find symbol around the value (can be ', " or nothing) and split the tag
$regexp = "/$attr_name\s*=\s*('|\")?.*/im";
preg_match ($regexp, $tag_content, $found);
if (isset($found[1])){
$quote = $found[1];
$regexp = "/(.*)$attr_name\s*=?\s*$quote([^$quote]*)$quote?\s?(.*)/is";
}else{
$regexp = "/(.*)$attr_name\s*=\s*(\S+)\s?(.*)/is";
}
if (!preg_match ($regexp, $tag_content, $found))
return $tag_content;
$tag_part_before_attribute = $found[1];
$attr_value = $found[2];
$tag_part_after_attribute = $found[3];
//convert relative address to absolute (if needed)
$new_attr_value = $this->convert_relative_link($attr_value);
//change the tag attribute value so the tag will point to the script,
//and the original URL becomes the variable value passed to the script
$new_attr_value = $this->link_url_to_script ($new_attr_value);
//compiling new tag contentents
//adding the beginning of the tag
$new_tag_content = $tag_part_before_attribute;
//adding new attribute
$new_tag_content .= $attr_name. "=". '"'.$new_attr_value.'"';
//adding the rest of the tag intact
$new_tag_content .= $tag_part_after_attribute;
return $new_tag_content;
}
// function recieves the URI from the tag attribute and checks if it is relative
// if so, function converts the URI to the absolute form
// using data on current URI from the class variable (array) $url
function convert_relative_link ($relative_url){
$regexp = "~^http://~i";
if (preg_match($regexp, $relative_url)){
return ($relative_url); // this is an absolute URL, no change needed
}
//attach relative link to the current URI's directory
$new_path = dirname($this->URI->path)."/". $relative_url;
//replace back and repetitive slashes with a single forward one
$new_path = preg_replace ("~((\\\\+)|/){2,}~", "/", $new_path);
//parse links to the upper directories
if (strpos($new_path, "/../") !== false){
$path_array = explode ("/", $new_path);
foreach ($path_array as $key=>$value){
if ($value == ".."){
if ($key > 2){
unset ($path_array[$key-1]);
}
unset ($path_array[$key]);
}
}
$new_path = implode ("/", $path_array);
}
//writing absolute url based on relative and base page addresses
$absolute_url = $this->URI->scheme.$this->URI->user.$this->URI->pass.
$this->URI->host.$this->URI->port_string.$new_path;
return $absolute_url;
}
//url from the web page becomes the attribute passed to the script
function link_url_to_script ($url){
global $HTTP_SERVER_VARS;
$script_url = "http://".$HTTP_SERVER_VARS['HTTP_HOST'].$HTTP_SERVER_VARS ['PHP_SELF'];
//detect fragment in the target URI
if ($fragment_pos = strpos($url, "#")){
$fragment = substr($url, $fragment_pos);
}else{
$fragment ="";
}
//encode target URI to be passed as a parameter
$point_to = urlencode($url);
$full_new_url = $script_url."?php_browser_uri=".$point_to.$fragment;
return $full_new_url;
}
//end of the class
}
?>
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