<img <b>src</b>="/image/fluffybunny.jpg" <b>title</b>="Harvey the bunny" <b>alt</b>="a cute little fluffy bunny" />我猜这应该用一些正则表达式来完成，但是由于标签的顺序可能会变化，并且我需要所有的标签，我不知道如何以优雅的方式解析它（我可以逐个字符地努力去做，但那很痛苦）。
$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');
}
使用正则表达式来解决这类问题是一个糟糕的主意，很可能会导致代码难以维护和不可靠。最好使用一个HTML解析器。
在这种情况下，最好将过程分为两个部分：
我假设您的文档不是严格的xHTML，因此无法使用XML解析器。例如，使用这个网页源代码：
/* 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)" />
[...]
)
)
$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"
)
)
[..]
)
)
首先，我们使用preg_match_all函数，该函数获取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[^>]+>
(alt|title|src)=("[^"]*")
alt=foo 或 alt='foo'。 - mgutt这里只提供一个使用PHP的XML功能完成任务的小例子：
$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'];
}
我使用了DOMDocument::loadHTML()方法，因为这个方法可以处理HTML语法，不强制输入文档成为XHTML。严格来说，转换成SimpleXMLElement并不是必须的，只是让使用xpath和xpath结果更加简单。
libxml_use_internal_errors(true);。您还可以使用libxml_get_errors()循环遍历这些XML错误。 - Matt如果它是XHTML，就像你的例子一样，你只需要使用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"
}
}
我使用 preg_match 来实现它。
在我的情况下，我有一个字符串，其中仅包含一个 <img> 标记（没有其他标记），我从 WordPress 中获取该字符串并尝试获取 src 属性，以便可以通过 timthumb 运行它。
// 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);
$pattern = '/title="([^"]*)"/';来提取标题或$pattern = '/alt="([^"]*)"/'; 来提取 alt。不幸的是，我的正则表达式能力还不足以一次性提取所有三个（alt/title/src）。<img src ='image.png'> - numediaweb// 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 $element->href . '<br>';
foreach($result[0] as $img_tag)
我已经阅读了这个页面上很多评论，抱怨使用dom解析器是不必要的开销。可能比纯粹的正则表达式调用更昂贵，但OP已经声明对于img标签中属性的顺序没有控制。这个事实导致了不必要的正则表达式模式复杂性。此外，使用dom解析器提供了可读性、可维护性和dom感知能力（正则表达式不具备dom感知能力）等其他好处。
我喜欢正则表达式，并回答了许多有关正则表达式的问题，但在处理有效的HTML时，很少有理由使用正则表达式而不是解析器。
在下面的演示中，请看一下DOMDocument如何轻松、干净地处理任意顺序的img标签属性以及引号混合（以及根本不引用）。还请注意，没有针对性的属性的标记完全没有影响--提供一个空字符串作为值。
代码：(演示)
$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 = " , $img->getAttribute('alt') , "\n";
echo "---\n";
}
输出：
IMG#0:
src = /image/fluffybunny.jpg
title = Harvey the bunny
alt = a cute little fluffy bunny
---
IMG#1:
src = /image/pricklycactus.jpg
title = Roger the cactus
alt = a big green prickly cactus
---
IMG#2:
src = /image/noisycockatoo.jpg
title = Polly the cockatoo
alt = an annoying white cockatoo
---
IMG#3:
src = somethingelse
title = something
alt =
---
以下是我从上述所有信息中拼凑出来的 PHP 函数，用于类似的目的，即动态调整图像标签的宽度和长度属性...可能有些笨拙，但似乎可靠地工作：
function ReSizeImagesInHTML($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;
}
这里是PHP的解决方案：
只需下载QueryPath，然后按照以下步骤操作：
$doc= qp($myHtmlDoc);
foreach($doc->xpath('//img') as $img) {
$src= $img->attr('src');
$title= $img->attr('title');
$alt= $img->attr('alt');
}
完成了，你做完了！