如何使用PHP从html中提取img src,title和alt?

时间:2008-09-26 08:33:06

标签: php html regex html-parsing html-content-extraction

我想创建一个页面,其中所有驻留在我网站上的图像都列有标题和替代表示。

我已经给我写了一个程序来查找和加载所有HTML文件,但现在我不知道如何从这个HTML中提取srctitlealt

<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny" />

我想这应该用一些正则表达式完成,但由于标签的顺序可能会有所不同,而且我需要所有这些,我真的不知道如何以优雅的方式解析它(我可以做到通过char方式的硬炭,但这很痛苦。)

10 个答案:

答案 0 :(得分:241)

$url="http://example.com";

$html = file_get_contents($url);

$doc = new DOMDocument();
@$doc->loadHTML($html);

$tags = $doc->getElementsByTagName('img');

foreach ($tags as $tag) {
       echo $tag->getAttribute('src');
}

答案 1 :(得分:191)

编辑:现在我知道了更好

使用regexp来解决这类问题的问题是a bad idea,并且很可能会导致无法维护和不可靠的代码。更好地使用HTML parser

使用regexp的解决方案

在这种情况下,最好将流程分为两部分:

  • 获取所有img标签
  • 提取元数据

我将假设您的doc不是xHTML严格的,因此您不能使用XML解析器。例如。使用此网页源代码:

/* preg_match_all match the regexp in all the $html string and output everything as 
an array in $result. "i" option is used to make it case insensitive */

preg_match_all('/<img[^>]+>/i',$html, $result); 

print_r($result);
Array
(
    [0] => Array
        (
            [0] => <img src="/Content/Img/stackoverflow-logo-250.png" width="250" height="70" alt="logo link to homepage" />
            [1] => <img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />
            [2] => <img class="vote-down" src="/content/img/vote-arrow-down.png" alt="vote down" title="This was not helpful (click again to undo)" />
            [3] => <img src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG" height=32 width=32 alt="gravatar image" />
            [4] => <img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />

[...]
        )

)

然后我们用循环获取所有img标记属性:

$img = array();
foreach( $result as $img_tag)
{
    preg_match_all('/(alt|title|src)=("[^"]*")/i',$img_tag, $img[$img_tag]);
}

print_r($img);

Array
(
    [<img src="/Content/Img/stackoverflow-logo-250.png" width="250" height="70" alt="logo link to homepage" />] => Array
        (
            [0] => Array
                (
                    [0] => src="/Content/Img/stackoverflow-logo-250.png"
                    [1] => alt="logo link to homepage"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                )

            [2] => Array
                (
                    [0] => "/Content/Img/stackoverflow-logo-250.png"
                    [1] => "logo link to homepage"
                )

        )

    [<img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />] => Array
        (
            [0] => Array
                (
                    [0] => src="/content/img/vote-arrow-up.png"
                    [1] => alt="vote up"
                    [2] => title="This was helpful (click again to undo)"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                    [2] => title
                )

            [2] => Array
                (
                    [0] => "/content/img/vote-arrow-up.png"
                    [1] => "vote up"
                    [2] => "This was helpful (click again to undo)"
                )

        )

    [<img class="vote-down" src="/content/img/vote-arrow-down.png" alt="vote down" title="This was not helpful (click again to undo)" />] => Array
        (
            [0] => Array
                (
                    [0] => src="/content/img/vote-arrow-down.png"
                    [1] => alt="vote down"
                    [2] => title="This was not helpful (click again to undo)"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                    [2] => title
                )

            [2] => Array
                (
                    [0] => "/content/img/vote-arrow-down.png"
                    [1] => "vote down"
                    [2] => "This was not helpful (click again to undo)"
                )

        )

    [<img src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG" height=32 width=32 alt="gravatar image" />] => Array
        (
            [0] => Array
                (
                    [0] => src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG"
                    [1] => alt="gravatar image"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                )

            [2] => Array
                (
                    [0] => "http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG"
                    [1] => "gravatar image"
                )

        )

   [..]
        )

)

Regexp是CPU密集型的,因此您可能希望缓存此页面。如果您没有缓存系统,可以使用ob_start并从文本文件加载/保存来调整自己的缓存系统。

这些东西是如何工作的?

首先,我们使用preg_ match_ all,这个函数可以获得与模式匹配的每个字符串,并将其输出到第三个参数中。

正则表达式:

<img[^>]+>

我们将其应用于所有html网页。它可以被读作以“<img”开头的每个字符串,包含非“&gt;” char并以&gt; 结束。

(alt|title|src)=("[^"]*")

我们在每个img标签上连续应用它。它可以被读作以“alt”,“title”或“src”开头的每个字符串,然后是“=”,然后是“”,一堆不是'“的字符串,以'''。在()之间隔离子字符串。

最后,每次你想要处理regexp时,都可以使用好的工具来快速测试它们。请检查此online regexp tester

编辑:回答第一条评论。

确实,我没有想到(希望很少)人使用单引号。

好吧,如果你只使用',只需替换所有“by”。

如果你混合两者。首先你应该打自己:-),然后尝试使用(“|')代替或”和[^ø]来代替[^“]。

答案 2 :(得分:64)

只是举一个使用PHP的XML功能来完成任务的小例子:

$doc=new DOMDocument();
$doc->loadHTML("<html><body>Test<br><img src=\"myimage.jpg\" title=\"title\" alt=\"alt\"></body></html>");
$xml=simplexml_import_dom($doc); // just to make xpath more simple
$images=$xml->xpath('//img');
foreach ($images as $img) {
    echo $img['src'] . ' ' . $img['alt'] . ' ' . $img['title'];
}

我确实使用了DOMDocument::loadHTML()方法,因为此方法可以处理HTML语法,并且不会强制输入文档为XHTML。严格地说,转换为SimpleXMLElement不是必需的 - 它只是使用xpath并且xpath结果更简单。

答案 3 :(得分:8)

如果它是XHTML,那么你的例子是,你只需要simpleXML。

<?php
$input = '<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny"/>';
$sx = simplexml_load_string($input);
var_dump($sx);
?>

输出:

object(SimpleXMLElement)#1 (1) {
  ["@attributes"]=>
  array(3) {
    ["src"]=>
    string(22) "/image/fluffybunny.jpg"
    ["title"]=>
    string(16) "Harvey the bunny"
    ["alt"]=>
    string(26) "a cute little fluffy bunny"
  }
}

答案 4 :(得分:5)

必须像这样编辑脚本

foreach( $result[0] as $img_tag)

因为preg_match_all返回数组数组

答案 5 :(得分:5)

您可以使用simplehtmldom。 simplehtmldom支持大多数jQuery选择器。下面给出一个例子

// Create DOM from URL or file
$html = file_get_html('http://www.google.com/');

// Find all images
foreach($html->find('img') as $element)
       echo $element->src . '<br>';

// Find all links
foreach($html->find('a') as $element)
       echo $element->href . '<br>'; 

答案 6 :(得分:3)

我用preg_match来做。

在我的情况下,我有一个字符串,其中包含我从Wordpress获得的一个<img>标记(并且没有其他标记),我试图获取src属性,以便我可以运行它timthumb。

// get the featured image
$image = get_the_post_thumbnail($photos[$i]->ID);

// get the src for that image
$pattern = '/src="([^"]*)"/';
preg_match($pattern, $image, $matches);
$src = $matches[1];
unset($matches);

在获取标题或替代品的模式中,您只需使用$pattern = '/title="([^"]*)"/';来获取标题,或使用$pattern = '/title="([^"]*)"/';来获取替代品。可悲的是,我的正则表达式并不足以通过一次传递来获取所有三个(alt / title / src)。

答案 7 :(得分:1)

这是一个PHP函数我为了类似的目的而从所有上述信息中蹒跚而行,即动态调整图像标签的宽度和长度属性...有点笨重,或许,但似乎可靠地工作:

function ReSizeImagesInHTML($HTMLContent,$MaximumWidth,$MaximumHeight) {

// find image tags
preg_match_all('/<img[^>]+>/i',$HTMLContent, $rawimagearray,PREG_SET_ORDER); 

// put image tags in a simpler array
$imagearray = array();
for ($i = 0; $i < count($rawimagearray); $i++) {
    array_push($imagearray, $rawimagearray[$i][0]);
}

// put image attributes in another array
$imageinfo = array();
foreach($imagearray as $img_tag) {

    preg_match_all('/(src|width|height)=("[^"]*")/i',$img_tag, $imageinfo[$img_tag]);
}

// combine everything into one array
$AllImageInfo = array();
foreach($imagearray as $img_tag) {

    $ImageSource = str_replace('"', '', $imageinfo[$img_tag][2][0]);
    $OrignialWidth = str_replace('"', '', $imageinfo[$img_tag][2][1]);
    $OrignialHeight = str_replace('"', '', $imageinfo[$img_tag][2][2]);

    $NewWidth = $OrignialWidth; 
    $NewHeight = $OrignialHeight;
    $AdjustDimensions = "F";

    if($OrignialWidth > $MaximumWidth) { 
        $diff = $OrignialWidth-$MaximumHeight; 
        $percnt_reduced = (($diff/$OrignialWidth)*100); 
        $NewHeight = floor($OrignialHeight-(($percnt_reduced*$OrignialHeight)/100)); 
        $NewWidth = floor($OrignialWidth-$diff); 
        $AdjustDimensions = "T";
    }

    if($OrignialHeight > $MaximumHeight) { 
        $diff = $OrignialHeight-$MaximumWidth; 
        $percnt_reduced = (($diff/$OrignialHeight)*100); 
        $NewWidth = floor($OrignialWidth-(($percnt_reduced*$OrignialWidth)/100)); 
        $NewHeight= floor($OrignialHeight-$diff); 
        $AdjustDimensions = "T";
    } 

    $thisImageInfo = array('OriginalImageTag' => $img_tag , 'ImageSource' => $ImageSource , 'OrignialWidth' => $OrignialWidth , 'OrignialHeight' => $OrignialHeight , 'NewWidth' => $NewWidth , 'NewHeight' => $NewHeight, 'AdjustDimensions' => $AdjustDimensions);
    array_push($AllImageInfo, $thisImageInfo);
}

// build array of before and after tags
$ImageBeforeAndAfter = array();
for ($i = 0; $i < count($AllImageInfo); $i++) {

    if($AllImageInfo[$i]['AdjustDimensions'] == "T") {
        $NewImageTag = str_ireplace('width="' . $AllImageInfo[$i]['OrignialWidth'] . '"', 'width="' . $AllImageInfo[$i]['NewWidth'] . '"', $AllImageInfo[$i]['OriginalImageTag']);
        $NewImageTag = str_ireplace('height="' . $AllImageInfo[$i]['OrignialHeight'] . '"', 'height="' . $AllImageInfo[$i]['NewHeight'] . '"', $NewImageTag);

        $thisImageBeforeAndAfter = array('OriginalImageTag' => $AllImageInfo[$i]['OriginalImageTag'] , 'NewImageTag' => $NewImageTag);
        array_push($ImageBeforeAndAfter, $thisImageBeforeAndAfter);
    }
}

// execute search and replace
for ($i = 0; $i < count($ImageBeforeAndAfter); $i++) {
    $HTMLContent = str_ireplace($ImageBeforeAndAfter[$i]['OriginalImageTag'],$ImageBeforeAndAfter[$i]['NewImageTag'], $HTMLContent);
}

return $HTMLContent;

}

答案 8 :(得分:0)

以下是PHP中的解决方案:

只需下载QueryPath,然后执行以下操作:

$doc= qp($myHtmlDoc);

foreach($doc->xpath('//img') as $img) {

   $src= $img->attr('src');
   $title= $img->attr('title');
   $alt= $img->attr('alt');

}

就是这样,你已经完成了!

答案 9 :(得分:0)

我已经阅读了本页上的许多评论,这些评论抱怨说使用dom解析器是不必要的开销。嗯,这可能比仅进行正则表达式调用更为昂贵,但是OP表示无法控制img标签中属性的顺序。这个事实导致不必要的正则表达式模式卷积。除此之外,使用dom解析器还具有可读性,可维护性和dom意识(正则表达式不是dom意识)的其他好处。

我喜欢正则表达式,并且回答了很多正则表达式问题,但是当处理有效的HTML时,很少有理由要在解析器上进行正则表达式。

在下面的演示中,了解如何简单,干净地使用DOMDocument以引号(和根本不引号)的混合顺序处理img标签属性。还要注意,没有目标属性的标记根本不会破坏-提供一个空字符串作为值。

代码:(Demo

$test = <<<HTML
<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny" />
<img src='/image/pricklycactus.jpg' title='Roger the cactus' alt='a big green prickly cactus' />
<p>This is irrelevant text.</p>
<img alt="an annoying white cockatoo" title="Polly the cockatoo" src="/image/noisycockatoo.jpg">
<img title=something src=somethingelse>
HTML;

libxml_use_internal_errors(true);  // silences/forgives complaints from the parser (remove to see what is generated)
$dom = new DOMDocument();
$dom->loadHTML($test);
foreach ($dom->getElementsByTagName('img') as $i => $img) {
    echo "IMG#{$i}:\n";
    echo "\tsrc = " , $img->getAttribute('src') , "\n";
    echo "\ttitle = " , $img->getAttribute('title') , "\n";
    echo "\talt = " , $img->getAttribute('alt') , "\n";
    echo "---\n";
}

输出:

IMG#0:
    src = /image/fluffybunny.jpg
    title = Harvey the bunny
    alt = a cute little fluffy bunny
---
IMG#1:
    src = /image/pricklycactus.jpg
    title = Roger the cactus
    alt = a big green prickly cactus
---
IMG#2:
    src = /image/noisycockatoo.jpg
    title = Polly the cockatoo
    alt = an annoying white cockatoo
---
IMG#3:
    src = somethingelse
    title = something
    alt = 
---

在专业代码中使用此技术将使您的脚本干净整洁,可以避免打h,希望您在其他地方工作的同事也更少。