How to add rel=“lightbox” only to links which are including an image and not the rest of the links? [duplicate]

问题

Lets say that (in php) we have a variable which has text, links and images :

<a href="myimage_big"><img src="myimage.jpg" alt="pic" title="pic" border="0" /></a>

and we want to add to every a href tag the rel="light" as follow :

<a rel="lightbox" href="myimage_big"><img src="myimage.jpg" alt="pic" title="pic" border="0" /></a>

If the name of the variable is lets say $mydata then with str_replace we can do as follow to solve our problem :

$mydata = str_replace('<img ', '<img rel="lightbox"', $mydata);

Till here is all right, but what about the rest of the a href links that are not including any photo :

par example,

<a href="link1.php">link_no1</a>
<a href="link2.php">link_no2</a>

etc ? To this kind of links that are not including any image but text then with our str_replace code will also have a rel="lightbox" attribute that is not correct and i dont want :

<a rel="lightbox" href="link1.php">link_no1</a>

So how we can apply the rel="lightbox" only to the links that are including some image and to those links that are not including any image to dont set the rel="lightbox" attribute ..!?

回答1:

Does this regex solve the problem?

$str = '<a href="myimage_big"><img src="myimage.jpg" /></a>';

$str = preg_replace('~<a(?=[^>]+>\s*<img)~','<a rel="lightbox"',$str);

echo htmlspecialchars($str);

Using a lookahead to check, if the <a ...> is followed by <img

回答2:

If you prefer to use a regular expression ...

$html = preg_replace('/(?<=<a)(?=[^>]*>[^<]*<img)/', ' rel="lightbox"', $html);

Although, I would consider using DOM and XPath ...

$doc = DOMDocument::loadHTML('
     <a href="myimage_big"><img src="myimage.jpg" alt="pic" title="pic" border="0" /></a>
     <a href="link1.php">link_no1</a>
     <a href="link2.php">link_no2</a>
     <a href="image.jpg"><img src="image1.jpg"></a>
');

$xpath = new DOMXPath($doc);
$links = $xpath->query('//a//img');

foreach($links as $link) { 
   $link->parentNode->setAttribute('rel', 'lightbox');
}

echo $doc->saveHTML();

来源：https://stackoverflow.com/questions/20767749/how-to-add-rel-lightbox-only-to-links-which-are-including-an-image-and-not-the

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php

html

regex

image