PHP implements recursive crawling of web page class instances_PHP tutorial

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class crawler{

private $_depth=5;

private $_urls=array();

function extract_links($url)

{

if(!$this->_started){

$this->_started=1;

$curr_depth=0;

}else{

$curr_depth ;

}

if($curr_depth<$this->_depth)

{

$data=file_get_contents($url);

if(preg_match_all('/((?:http|https)://(?:www.)*(?:[a-zA-Z0-9_-]{1,15}. [a-zA-Z0-9_]{1,}){1,}(?:[a-zA-Z0-9_/.-?&:%,!;]*))/',$data,$urls12))

{

foreach($urls12[0] as $k=>$v){

$check=get_headers($v,1);

if(strstr($v,$url) && $check[0]=='HTTP/1.1 200 OK' && !array_search($v,$this->_urls) && $curr_depth<$this->_depth){

$this->_urls[]=$v;

$this->extract_links($v);

}

}

}

}

return $this->_urls;

}

}

?>