Question

Php Masters，

这是从谷歌抓取链接的代码。

<?php

# Use the Curl extension to query Google and get back a page of results
$url = "http://www.google.com";
$ch = curl_init();
$timeout = 5;
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
$html = curl_exec($ch);
curl_close($ch);

# Create a DOM parser object
$dom = new DOMDocument();

# Parse the HTML from Google.
# The @ before the method call suppresses any warnings that
# loadHTML might throw because of invalid HTML in the page.
@$dom->loadHTML($html);

# Iterate over all the <a> tags
foreach($dom->getElementsByTagName('a') as $link) {
        # Show the <a href>
        echo $link->getAttribute('href');
        echo "<br />";

?>

它回应了这样的结果：

https://www.google.com/webhp?tab=ww
http://www.google.com/imghp?hl=bn&tab=wi

现在，我还是一个学习者，需要你的帮助。我想转换上面的代码，以便使用DOM，它能够从所选网页上的所有链接中提取所有网址及其锚文本，无论链接的格式如何。格式如：

<a href="http://example1.com">Test 1</a>
<a class="foo" id="bar" href="http://example2.com">Test 2</a>
<a onclick="foo();" id="bar" href="http://example3.com">Test 3</a>

锚文本应位于每个提取的网址下方。并且每个列出的项目之间应该有一条线。如：

http://stackoverflow.com<br>
A programmer's forum<br>
<br>
http://google.com<br>
A searchengine<br>
<br>
http://yahoo.com<br>
An Index<br>
<br>

等等。我也很欣赏来自执行相同结果的优秀人员的cURL版本（不使用DOM）。这个cURL并没有完全按照我想要的方式工作：

<?php

$curl = curl_init('http://stackoverflow.com/');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);

$page = curl_exec($curl);

if(curl_errno($curl)) // check for execution errors
{
    echo 'Scraper error: ' . curl_error($curl);
    exit;
}

curl_close($curl);

$regex = '<\s*a\s+[^>]*href\s*=\s*[\"']?([^\"' >]+)[\"' >]';
if ( preg_match($regex, $page, $list) )
    echo $list[0];
else 
    print "Not found"; 

?>

如果没有正则表达式，使用cURL（不使用DOM）可以实现这一点吗？我想看一个正则表达式样本和一个没有正则表达式的样本。最后，我真的不想使用有限的函数，比如get_file（）等。

谢谢！

第一次编辑：这不起作用：

<?php

# Use the Curl extension to query Google and get back a page of results
$url = "http://fiverr.com/";
$ch = curl_init();
$timeout = 5;
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
$html = curl_exec($ch);
curl_close($ch);

# Create a DOM parser object
$dom = new DOMDocument();

# Parse the HTML from Devshed Forum.
# The @ before the method call suppresses any warnings that
# loadHTML might throw because of invalid HTML in the page.
@$dom->loadHTML($html);

# Iterate over all the <a> tags
foreach($dom->getElementsByTagName('a') as $link) {
        # Show the <a href>
        echo $link->getAttribute('href');
        echo "<br />";
        echo $link->nodeValue;      
}

?>

我看到一个完整的白色空白页面。没有回音。

第二次编辑：我更新了脚本并看到了这些错误：

**Warning: DOMDocument::loadHTML(): Tag header invalid in Entity, line: 97 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 119 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 119 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag nav invalid in Entity, line: 123 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 149 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 149 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 159 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 159 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 162 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 162 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 168 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 168 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 174 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 174 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 179 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 179 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): htmlParseEntityRef: expecting ';' in Entity, line: 184 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): htmlParseEntityRef: expecting ';' in Entity, line: 185 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): htmlParseEntityRef: expecting ';' in Entity, line: 348 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 352 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag g invalid in Entity, line: 352 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 352 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 352 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 352 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 352 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 356 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 356 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 358 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 358 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): htmlParseEntityRef: expecting ';' in Entity, line: 361 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): htmlParseEntityRef: expecting ';' in Entity, line: 838 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 845 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag g invalid in Entity, line: 845 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 845 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 845 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 845 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 845 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 848 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 848 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 851 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag g invalid in Entity, line: 851 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 851 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 851 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): ID display-name already defined in Entity, line: 895 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): ID m-address already defined in Entity, line: 899 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 1155 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 1155 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag footer invalid in Entity, line: 1168 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 1172 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag g invalid in Entity, line: 1172 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 1172 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 1172 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag nav invalid in Entity, line: 1175 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag svg invalid in Entity, line: 1208 in C:\xampp\htdocs\cURL\crawler.php on line 194
Warning: DOMDocument::loadHTML(): Tag path invalid in Entity, line: 1208 in C:\xampp\htdocs\cURL\crawler.php on line 194**

更新：

<?php

/*
Using PHP's DOM functions to
  fetch hyperlinks and their anchor text
*/


$dom = new DOMDocument;
$dom->loadHTML(file_get_contents('https://stackoverflow.com/questions/50381348/extract-urls-anchor-texts-from-links-on-a-webpage-fetched-by-php-or-curl')); 

// echo Links and their anchor text
echo '<pre>';
echo "Link\tAnchor\n";
foreach($dom->getElementsByTagName('a') as $link) {
    $href = $link->getAttribute('href');
    $anchor = $link->nodeValue;
    echo $href,"\t",$anchor,"\n";
}
echo '</pre>';

?>

第三次编辑：好。到目前为止，Luis Munoz的样本对我有用。但是，他的样本以及我的原始样本并不是基于抓取页面上找到的链接之后的爬虫。因此，现在希望扩展我们脚本的功能，以便抓取器跟踪在获取的页面上找到的链接。以下是我在2种不同方式下尝试构建跟踪爬虫的简单链接。我要做的是学习构建一个简单的网络爬虫，它遵循链接并提取随后在新页面上找到的链接。

的步骤：所以一开始，我会先给它一个网址。然后它将获取该页面并将所有链接提取到单个数组中并回显提取的链接，以便在每个页面加载时，您只能看到提取的链接被回显。然后，它将获取每个链接页面并将其所有链接提取到单个数组中，并同样回显提取的链接。它将执行此操作，直到达到它的最大链接深层设置。

尝试1

<?php 

include('simple_html_dom.php'); 

$current_link_crawling_level = 0; 
$link_crawling_level_max = 2;

if($current_link_crawling_level == $link_crawling_level_max)
{
    echo "link crawling depth level reached!"; 
    sleep(5);
    exit(); 
}
else
{
    $url = 'http://php.net/manual-lookup.php? 
pattern=str_get_html&scope=quickref'; 
    $curl = curl_init($url); 
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1); 
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0); 
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0); 
    $response_string = curl_exec($curl); 

    $html = str_get_html($response_string);

    $current_link_crawling_level++; 

    //to fetch all hyperlinks from the webpage 
    $links = array(); 
    foreach($html->find('a') as $a) 
    { 
        $links[] = $a->href; 
        echo "Value: $a<br />\n"; 
        print_r($links); 

        sleep(1);

        $url = '$value'; 
        $curl = curl_init($a); 
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); 
        curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1); 
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0); 
        curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0); 
        $response_string = curl_exec($curl); 

        $html = str_get_html($response_string);

        $current_link_crawling_level++; 

        //to fetch all hyperlinks from the webpage 
        $links = array(); 
        foreach($html->find('a') as $a) 
        { 
            $links[] = $a->href; 
            echo "Value: $a<br />\n";
            print_r($links); 

            sleep(1);           
        } 
    echo "Value: $a<br />\n";
    print_r($links); 
    }
}

?>

第二次尝试：

<?php 

include('simple_html_dom.php'); 

$current_link_crawling_level = 0; 
$link_crawling_level_max = 2;

if($current_link_crawling_level == $link_crawling_level_max)
{
    echo "link crawling depth level reached!"; 
    sleep(5);
    exit(); 
}
else
{
    $url = 'http://php.net/manual-lookup.php?pattern=str_get_html&scope=quickref'; 
    $curl = curl_init($url); 
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1); 
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0); 
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0); 
    $response_string = curl_exec($curl); 

    $html = str_get_html($response_string);

    $current_link_crawling_level++; 

    //to fetch all hyperlinks from the webpage 
    // Hide HTML warnings
    libxml_use_internal_errors(true);
    $dom = new DOMDocument;
    if($dom->loadHTML($html, LIBXML_NOWARNING))
    {
        // echo Links and their anchor text
        echo '<pre>';
        echo "Link\tAnchor\n";
        foreach($dom->getElementsByTagName('a') as $link) 
        {
            $href = $link->getAttribute('href');
            $anchor = $link->nodeValue;
            echo $href,"\t",$anchor,"\n";

            sleep(1);

            $url = 'http://php.net/manual-lookup.php?pattern=str_get_html&scope=quickref'; 
            $curl = curl_init($url); 
            curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); 
            curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1); 
            curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0); 
            curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0); 
            $response_string = curl_exec($curl); 

            $html = str_get_html($response_string);

            $current_link_crawling_level++; 

            //to fetch all hyperlinks from the webpage 
            // Hide HTML warnings
            libxml_use_internal_errors(true);
            $dom = new DOMDocument;
            if($dom->loadHTML($html, LIBXML_NOWARNING))
            {
                // echo Links and their anchor text
                echo '<pre>';
                echo "Link\tAnchor\n";
                foreach($dom->getElementsByTagName('a') as $link) 
                {
                    $href = $link->getAttribute('href');
                    $anchor = $link->nodeValue;
                    echo $href,"\t",$anchor,"\n";

                    sleep(1);
                }
                echo '</pre>';
            }
            else
            {
                echo "Failed to load html.";
            }
        }
    }
    else
    {
        echo "Failed to load html.";
    }
}
?>

我很感激任何代码示例对初学者来说非常简单。更好，如果是程序风格，因为我是初学者。

谢谢！

Answer 1

我们使用cURL代替file_get_contents，因为它是处理HTTPS请求的更好选择。此外，添加警告抑制控件以避免有关HTML损坏的消息

<?php

/*
Using PHP's DOM functions to
fetch hyperlinks and their anchor text
*/

$url = 'https://stackoverflow.com/questions/50381348/extract-urls-anchor-texts-from-links-on-a-webpage-fetched-by-php-or-curl';
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0);
$data = curl_exec($curl);

// Hide HTML warnings
libxml_use_internal_errors(true);
$dom = new DOMDocument;
if($dom->loadHTML($data, LIBXML_NOWARNING)){
    // echo Links and their anchor text
    echo '<pre>';
    echo "Link\tAnchor\n";
    foreach($dom->getElementsByTagName('a') as $link) {
        $href = $link->getAttribute('href');
        $anchor = $link->nodeValue;
        echo $href,"\t",$anchor,"\n";
    }
    echo '</pre>';
}else{
    echo "Failed to load html.";

}
?>

提取网址＆amp;来自Php或cURL提供的网页上链接的锚文本

1 个答案: