如何在PHP中实现Web scraper？

什么内置的PHP函数对Web抓取有用？有什么好的资源(网络或打印),以加快使用PHP进行网络抓取的速度？

1> tyshock..：

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刮痧通常包括3个步骤:

首先,您将请求获取或发送到指定的URL

接下来,您将收到作为响应返回的html

最后你解析那个html你要抓的文字.

要完成步骤1和2,下面是一个简单的php类,它使用Curl来使用GET或POST获取网页.在您获得HTML后,您只需使用正则表达式通过解析您想要删除的文本来完成步骤3.

对于正则表达式,我最喜欢的教程网站如下: 正则表达式教程

我最喜欢使用RegExs的程序是Regex Buddy.即使您无意购买,我也会建议您尝试该产品的演示.它是一个非常宝贵的工具,甚至可以为您使用您选择的语言(包括php)制作的正则表达式生成代码.

用法:

$curl = new Curl();
$html = $curl->get("http://www.google.com");

// now, do your regex work against $html

PHP类:

cookieJar = $cookieJarFile;
    }

    function setup()
    {


        $header = array();
        $header[0] = "Accept: text/xml,application/xml,application/xhtml+xml,";
        $header[0] .= "text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5";
        $header[] =  "Cache-Control: max-age=0";
        $header[] =  "Connection: keep-alive";
        $header[] = "Keep-Alive: 300";
        $header[] = "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7";
        $header[] = "Accept-Language: en-us,en;q=0.5";
        $header[] = "Pragma: "; // browsers keep this blank.


        curl_setopt($this->curl, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows; U; Windows NT 5.2; en-US; rv:1.8.1.7) Gecko/20070914 Firefox/2.0.0.7');
        curl_setopt($this->curl, CURLOPT_HTTPHEADER, $header);
        curl_setopt($this->curl,CURLOPT_COOKIEJAR, $this->cookieJar); 
        curl_setopt($this->curl,CURLOPT_COOKIEFILE, $this->cookieJar);
        curl_setopt($this->curl,CURLOPT_AUTOREFERER, true);
        curl_setopt($this->curl,CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($this->curl,CURLOPT_RETURNTRANSFER, true);  
    }


    function get($url)
    { 
        $this->curl = curl_init($url);
        $this->setup();

        return $this->request();
    }

    function getAll($reg,$str)
    {
        preg_match_all($reg,$str,$matches);
        return $matches[1];
    }

    function postForm($url, $fields, $referer='')
    {
        $this->curl = curl_init($url);
        $this->setup();
        curl_setopt($this->curl, CURLOPT_URL, $url);
        curl_setopt($this->curl, CURLOPT_POST, 1);
        curl_setopt($this->curl, CURLOPT_REFERER, $referer);
        curl_setopt($this->curl, CURLOPT_POSTFIELDS, $fields);
        return $this->request();
    }

    function getInfo($info)
    {
        $info = ($info == 'lasturl') ? curl_getinfo($this->curl, CURLINFO_EFFECTIVE_URL) : curl_getinfo($this->curl, $info);
        return $info;
    }

    function request()
    {
        return curl_exec($this->curl);
    }
}

?>

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嗯,用正则表达式解析html是......好吧,我只想让这个人解释一下:http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454

2> Salman von A..：

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我推荐Goutte,一个简单的PHP Web Scraper.

用法示例: -

创建一个Goutte客户端实例(扩展 Symfony\Component\BrowserKit\Client):

use Goutte\Client;

$client = new Client();

使用request()方法发出请求:

$crawler = $client->request('GET', 'http://www.symfony-project.org/');

该request方法返回一个Crawlerobject(Symfony\Component\DomCrawler\Crawler).

点击链接:

$link = $crawler->selectLink('Plugins')->link();
$crawler = $client->click($link);

提交表格:

$form = $crawler->selectButton('sign in')->form();
$crawler = $client->submit($form, array('signin[username]' => 'fabien', 'signin[password]' => 'xxxxxx'));

提取数据:

$nodes = $crawler->filter('.error_list');

if ($nodes->count())
{
  die(sprintf("Authentification error: %s\n", $nodes->text()));
}

printf("Nb tasks: %d\n", $crawler->filter('#nb_tasks')->text());

3> Joe Niland..：

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ScraperWiki是一个非常有趣的项目.帮助您使用Python,Ruby或PHP在线构建scraper - 我能够在几分钟内完成一次简单的尝试.