如何用PHP制作一个简单的爬虫程序?

无聊的。不要 parse HTML with regexes .

<?php
function crawl_page($url, $depth = 5)
{
    static $seen = array();
    if (isset($seen[$url]) || $depth === 0) {
        return;
    }

    $seen[$url] = true;

    $dom = new DOMDocument('1.0');
    @$dom->loadHTMLFile($url);

    $anchors = $dom->getElementsByTagName('a');
    foreach ($anchors as $element) {
        $href = $element->getAttribute('href');
        if (0 !== strpos($href, 'http')) {
            $path = '/' . ltrim($href, '/');
            if (extension_loaded('http')) {
                $href = http_build_url($url, array('path' => $path));
            } else {
                $parts = parse_url($url);
                $href = $parts['scheme'] . '://';
                if (isset($parts['user']) && isset($parts['pass'])) {
                    $href .= $parts['user'] . ':' . $parts['pass'] . '@';
                }
                $href .= $parts['host'];
                if (isset($parts['port'])) {
                    $href .= ':' . $parts['port'];
                }
                $href .= dirname($parts['path'], 1).$path;
            }
        }
        crawl_page($href, $depth - 1);
    }
    echo "URL:",$url,PHP_EOL,"CONTENT:",PHP_EOL,$dom->saveHTML(),PHP_EOL,PHP_EOL;
}
crawl_page("http://hobodave.com", 2);

我修复了Tatu版本中的一些bug(现在可以使用相对URL)。

编辑: 我添加了一个新的功能,防止它跟随同一个URL两次。

现在将输出回显到标准输出,以便您可以将其重定向到所需的任何文件

编辑: 修正了乔治在回答中指出的错误。相对url将不再附加到url路径的末尾,而是覆盖它。多亏了乔治。请注意,George的回答没有考虑以下任何因素:https、user、pass或port。如果你有 http PECL扩展加载这是非常简单的使用 http_build_url

下面是我基于上述示例/答案的实现。

1. 它是基于类的
3. 支持HTTP身份验证
4. 跳过不属于基本域的Url
5. 返回每个页面的Http头响应代码
6. 每页的返回时间

爬网类:

class crawler
{
    protected $_url;
    protected $_depth;
    protected $_host;
    protected $_useHttpAuth = false;
    protected $_user;
    protected $_pass;
    protected $_seen = array();
    protected $_filter = array();

    public function __construct($url, $depth = 5)
    {
        $this->_url = $url;
        $this->_depth = $depth;
        $parse = parse_url($url);
        $this->_host = $parse['host'];
    }

    protected function _processAnchors($content, $url, $depth)
    {
        $dom = new DOMDocument('1.0');
        @$dom->loadHTML($content);
        $anchors = $dom->getElementsByTagName('a');

        foreach ($anchors as $element) {
            $href = $element->getAttribute('href');
            if (0 !== strpos($href, 'http')) {
                $path = '/' . ltrim($href, '/');
                if (extension_loaded('http')) {
                    $href = http_build_url($url, array('path' => $path));
                } else {
                    $parts = parse_url($url);
                    $href = $parts['scheme'] . '://';
                    if (isset($parts['user']) && isset($parts['pass'])) {
                        $href .= $parts['user'] . ':' . $parts['pass'] . '@';
                    }
                    $href .= $parts['host'];
                    if (isset($parts['port'])) {
                        $href .= ':' . $parts['port'];
                    }
                    $href .= $path;
                }
            }
            // Crawl only link that belongs to the start domain
            $this->crawl_page($href, $depth - 1);
        }
    }

    protected function _getContent($url)
    {
        $handle = curl_init($url);
        if ($this->_useHttpAuth) {
            curl_setopt($handle, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
            curl_setopt($handle, CURLOPT_USERPWD, $this->_user . ":" . $this->_pass);
        }
        // follows 302 redirect, creates problem wiht authentication
//        curl_setopt($handle, CURLOPT_FOLLOWLOCATION, TRUE);
        // return the content
        curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);

        /* Get the HTML or whatever is linked in $url. */
        $response = curl_exec($handle);
        // response total time
        $time = curl_getinfo($handle, CURLINFO_TOTAL_TIME);
        /* Check for 404 (file not found). */
        $httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);

        curl_close($handle);
        return array($response, $httpCode, $time);
    }

    protected function _printResult($url, $depth, $httpcode, $time)
    {
        ob_end_flush();
        $currentDepth = $this->_depth - $depth;
        $count = count($this->_seen);
        echo "N::$count,CODE::$httpcode,TIME::$time,DEPTH::$currentDepth URL::$url <br>";
        ob_start();
        flush();
    }

    protected function isValid($url, $depth)
    {
        if (strpos($url, $this->_host) === false
            || $depth === 0
            || isset($this->_seen[$url])
        ) {
            return false;
        }
        foreach ($this->_filter as $excludePath) {
            if (strpos($url, $excludePath) !== false) {
                return false;
            }
        }
        return true;
    }

    public function crawl_page($url, $depth)
    {
        if (!$this->isValid($url, $depth)) {
            return;
        }
        // add to the seen URL
        $this->_seen[$url] = true;
        // get Content and Return Code
        list($content, $httpcode, $time) = $this->_getContent($url);
        // print Result for current Page
        $this->_printResult($url, $depth, $httpcode, $time);
        // process subPages
        $this->_processAnchors($content, $url, $depth);
    }

    public function setHttpAuth($user, $pass)
    {
        $this->_useHttpAuth = true;
        $this->_user = $user;
        $this->_pass = $pass;
    }

    public function addFilterPath($path)
    {
        $this->_filter[] = $path;
    }

    public function run()
    {
        $this->crawl_page($this->_url, $this->_depth);
    }
}

// USAGE
$startURL = 'http://YOUR_URL/';
$depth = 6;
$username = 'YOURUSER';
$password = 'YOURPASS';
$crawler = new crawler($startURL, $depth);
$crawler->setHttpAuth($username, $password);
// Exclude path with the following structure to be processed 
$crawler->addFilterPath('customer/account/login/referer');
$crawler->run();

查看PHP爬虫

http://sourceforge.net/projects/php-crawler/

function crawl_page($url, $depth = 5) {
    if($depth > 0) {
        $html = file_get_contents($url);

        preg_match_all('~<a.*?href="(.*?)".*?>~', $html, $matches);

        foreach($matches[1] as $newurl) {
            crawl_page($newurl, $depth - 1);
        }

        file_put_contents('results.txt', $newurl."\n\n".$html."\n\n", FILE_APPEND);
    }
}

crawl_page('http://www.domain.com/index.php', 5);

该函数将从页面获取内容,然后爬网所有找到的链接并将内容保存到“results.txt”。这些函数接受第二个参数depth,它定义了链接应该遵循的时间长度。如果只想解析给定页面中的链接,请在此处传递1。

既然可以使用PHP,为什么还要使用PHP呢 wget

wget -r -l 1 http://www.example.com

有关如何解析内容,请参阅 Best Methods to parse HTML 并使用搜索功能 examples . 如何解析HTML之前已经回答过多次了。

只需对 hobodave's 代码,这里是一个可以用来抓取页面的代码片段。这需要在服务器中启用curl扩展。

<?php
//set_time_limit (0);
function crawl_page($url, $depth = 5){
$seen = array();
if(($depth == 0) or (in_array($url, $seen))){
    return;
}   
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_TIMEOUT, 30);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
$result = curl_exec ($ch);
curl_close ($ch);
if( $result ){
    $stripped_file = strip_tags($result, "<a>");
    preg_match_all("/<a[\s]+[^>]*?href[\s]?=[\s\"\']+"."(.*?)[\"\']+.*?>"."([^<]+|.*?)?<\/a>/", $stripped_file, $matches, PREG_SET_ORDER ); 
    foreach($matches as $match){
        $href = $match[1];
            if (0 !== strpos($href, 'http')) {
                $path = '/' . ltrim($href, '/');
                if (extension_loaded('http')) {
                    $href = http_build_url($href , array('path' => $path));
                } else {
                    $parts = parse_url($href);
                    $href = $parts['scheme'] . '://';
                    if (isset($parts['user']) && isset($parts['pass'])) {
                        $href .= $parts['user'] . ':' . $parts['pass'] . '@';
                    }
                    $href .= $parts['host'];
                    if (isset($parts['port'])) {
                        $href .= ':' . $parts['port'];
                    }
                    $href .= $path;
                }
            }
            crawl_page($href, $depth - 1);
        }
}   
echo "Crawled {$href}";
}   
crawl_page("http://www.sitename.com/",3);
?>

我已经在本文中解释了本教程 crawler script tutorial

<?php
function crawl_page($url, $depth = 5)
{
  static $seen = array();
  if (isset($seen[$url]) || $depth === 0) {
    return;
  }

  $seen[$url] = true;

  $dom = new DOMDocument('1.0');
  @$dom->loadHTMLFile($url);

  $anchors = $dom->getElementsByTagName('a');
  foreach ($anchors as $element) {
    $href = $element->getAttribute('href');
    if (0 !== strpos($href, 'http')) {
       /* this is where I changed hobodave's code */
        $host = "http://".parse_url($url,PHP_URL_HOST);
        $href = $host. '/' . ltrim($href, '/');
    }
    crawl_page($href, $depth - 1);
  }

  echo "New Page:<br /> ";
  echo "URL:",$url,PHP_EOL,"<br />","CONTENT:",PHP_EOL,$dom->saveHTML(),PHP_EOL,PHP_EOL,"  <br /><br />";
}

crawl_page("http://hobodave.com/", 5);
?>

正如前面提到的,有很多爬虫框架可以定制,但是如果你所做的事情像你提到的那样简单,你可以很容易地从头开始。

删除链接: http://www.phpro.org/examples/Get-Links-With-DOM.html

将结果转储到文件: http://www.tizag.com/phpT/filewrite.php

<?php
function crawl_page($url, $depth = 5)
{
  $parts = parse_url($url);
  if(array_key_exists('fragment', $parts)){
    unset($parts['fragment']);
    $url = http_build_url($parts);
  }

  static $seen = array();
  ...

然后您还可以省略 $parts = parse_url($url);

你可以试试这个,也许对你有帮助

$search_string = 'american golf News: Fowler beats stellar field in Abu Dhabi';
$html = file_get_contents(url of the site);
$dom = new DOMDocument;
$titalDom = new DOMDocument;
$tmpTitalDom = new DOMDocument;
libxml_use_internal_errors(true);
@$dom->loadHTML($html);
libxml_use_internal_errors(false);
$xpath = new DOMXPath($dom);
$videos = $xpath->query('//div[@class="primary-content"]');
foreach ($videos as $key => $video) {
$newdomaindom = new DOMDocument;    
$newnode = $newdomaindom->importNode($video, true);
$newdomaindom->appendChild($newnode);
@$titalDom->loadHTML($newdomaindom->saveHTML());
$xpath1 = new DOMXPath($titalDom);
$titles = $xpath1->query('//div[@class="listingcontainer"]/div[@class="list"]');
if(strcmp(preg_replace('!\s+!',' ',  $titles->item(0)->nodeValue),$search_string)){     
    $tmpNode = $tmpTitalDom->importNode($video, true);
    $tmpTitalDom->appendChild($tmpNode);
    break;
}
}
echo $tmpTitalDom->saveHTML();

谢谢你@hobodave。

然而,我发现你的代码有两个弱点。 为了得到“主机”段,对原始url的解析在第一个斜杠处停止。这假定所有相关链接都从根目录开始。这只是有时候是真的。

original url   :  http://example.com/game/index.html
href in <a> tag:  highscore.html
author's intent:  http://example.com/game/highscore.html  <-200->
crawler result :  http://example.com/highscore.html       <-404->

通过在最后一个斜杠而不是第一个斜杠处打断来修复此问题

$depth 不是真正跟踪递归深度,而是跟踪 递归的第一级。

如果我相信这个页面正在被积极使用,我可能会调试第二个版本,但我怀疑我现在写的文本永远不会被任何人阅读,无论是人类还是机器人,因为这个版本已经有六年了,我甚至没有足够的声誉通过对他的代码进行注释直接通知+hobodave这些缺陷。无论如何,谢谢你。

我想出了下面的蜘蛛代码。 PHP - Is the there a safe way to perform deep recursion? 似乎相当快。。。。

    <?php
function  spider( $base_url , $search_urls=array() ) {
    $queue[] = $base_url;
    $done           =   array();
    $found_urls     =   array();
    while($queue) {
            $link = array_shift($queue);
            if(!is_array($link)) {
                $done[] = $link;
                foreach( $search_urls as $s) { if (strstr( $link , $s )) { $found_urls[] = $link; } }
                if( empty($search_urls)) { $found_urls[] = $link; }
                if(!empty($link )) {
echo 'LINK:::'.$link;
                      $content =    file_get_contents( $link );
//echo 'P:::'.$content;
                    preg_match_all('~<a.*?href="(.*?)".*?>~', $content, $sublink);
                    if (!in_array($sublink , $done) && !in_array($sublink , $queue)  ) {
                           $queue[] = $sublink;
                    }
                }
            } else {
                    $result=array();
                    $return = array();
                    // flatten multi dimensional array of URLs to one dimensional.
                    while(count($link)) {
                         $value = array_shift($link);
                         if(is_array($value))
                             foreach($value as $sub)
                                $link[] = $sub;
                         else
                               $return[] = $value;
                     }
                     // now loop over one dimensional array.
                     foreach($return as $link) {
                                // echo 'L::'.$link;
                                // url may be in form <a href.. so extract what's in the href bit.
                                preg_match_all('/<a[^>]+href=([\'"])(?<href>.+?)\1[^>]*>/i', $link, $result);
                                if ( isset( $result['href'][0] )) { $link = $result['href'][0]; }
                                // add the new URL to the queue.
                                if( (!strstr( $link , "http")) && (!in_array($base_url.$link , $done)) && (!in_array($base_url.$link , $queue)) ) {
                                     $queue[]=$base_url.$link;
                                } else {
                                    if ( (strstr( $link , $base_url  ))  && (!in_array($base_url.$link , $done)) && (!in_array($base_url.$link , $queue)) ) {
                                         $queue[] = $link;
                                    }
                                }
                      }
            }
    }


    return $found_urls;
}    


    $base_url       =   'https://www.houseofcheese.co.uk/';
    $search_urls    =   array(  $base_url.'acatalog/' );
    $done = spider( $base_url  , $search_urls  );

    //
    // RESULT
    //
    //
    echo '<br /><br />';
    echo 'RESULT:::';
    foreach(  $done as $r )  {
        echo 'URL:::'.$r.'<br />';
    }

值得记住的是,在抓取外部链接时(我很欣赏OP与用户自己的页面相关),您应该知道robots.txt。我发现了以下几点,希望能有所帮助 http://www.the-art-of-web.com/php/parse-robots/ .

我创建了一个小类,从提供的url获取数据,然后提取您选择的html元素。该类使用CURL和DOMDocument。

class crawler {


   public static $timeout = 2;
   public static $agent   = 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)';


   public static function http_request($url) {
      $ch = curl_init();
      curl_setopt($ch, CURLOPT_URL,            $url);
      curl_setopt($ch, CURLOPT_USERAGENT,      self::$agent);
      curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, self::$timeout);
      curl_setopt($ch, CURLOPT_TIMEOUT,        self::$timeout);
      curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
      $response = curl_exec($ch);
      curl_close($ch);
      return $response;
   }


   public static function strip_whitespace($data) {
      $data = preg_replace('/\s+/', ' ', $data);
      return trim($data);
   }


   public static function extract_elements($tag, $data) {
      $response = array();
      $dom      = new DOMDocument;
      @$dom->loadHTML($data);
      foreach ( $dom->getElementsByTagName($tag) as $index => $element ) {
         $response[$index]['text'] = self::strip_whitespace($element->nodeValue);
         foreach ( $element->attributes as $attribute ) {
            $response[$index]['attributes'][strtolower($attribute->nodeName)] = self::strip_whitespace($attribute->nodeValue);
         }
      }
      return $response;
   }


}

用法示例:

$data  = crawler::http_request('https://stackoverflow.com/questions/2313107/how-do-i-make-a-simple-crawler-in-php');
$links = crawler::extract_elements('a', $data);
if ( count($links) > 0 ) {
   file_put_contents('links.json', json_encode($links, JSON_PRETTY_PRINT));
}

答复示例:

[
    {
        "text": "Stack Overflow",
        "attributes": {
            "href": "https:\/\/stackoverflow.com",
            "class": "-logo js-gps-track",
            "data-gps-track": "top_nav.click({is_current:false, location:2, destination:8})"
        }
    },
    {
        "text": "Questions",
        "attributes": {
            "id": "nav-questions",
            "href": "\/questions",
            "class": "-link js-gps-track",
            "data-gps-track": "top_nav.click({is_current:true, location:2, destination:1})"
        }
    },
    {
        "text": "Developer Jobs",
        "attributes": {
            "id": "nav-jobs",
            "href": "\/jobs?med=site-ui&ref=jobs-tab",
            "class": "-link js-gps-track",
            "data-gps-track": "top_nav.click({is_current:false, location:2, destination:6})"
        }
    }
]

这是个老问题。从那以后发生了很多好事。这是我在这个话题上的两分钱:

1. 要准确跟踪访问的页面,您必须首先规范化URI。标准化算法包括多个步骤:

   • GET http://www.example.com/query?id=111&cat=222 GET http://www.example.com/query?cat=222&id=111

   • 转换空路径。 例子: http://example.org → http://example.org/

   • 例子: http://example.org/a%c2%B1b → http://example.org/a%C2%B1b

   • 删除不必要的点段。 例子: http://example.org/../a/b/../c/./d.html → http://example.org/a/c/d.html

2. 不仅 <a> href 属性 <area> 标签上也有 https://html.com/tags/area/ <面积> 标签也是。

4. 善待网站所有者。

如果你不想处理这个问题,试试看 Crawlzone https://www.codementor.io/zstate/this-is-how-i-crawl-n98s6myxm