PHP regex to check if image is wrapped with a tag

Question

I am creating a wordpress function and need to determine whether an image in the content is wrapped with an a tag that contains a link to a PDF or DOC file e.g.

<a href="www.site.com/document.pdf"><img src="../images/image.jpg" /></a>

How would I go about doing this with PHP?

Thanks

Have a look [here](http://stackoverflow.com/questions/3577641/how-to-parse-and-process-html-xml), pick your favorite approach and then analyze all the links you could find in the text. Regular expressions are usually the wrong solution to a parsing problem. — Till Helge, Apr 18 '13 at 10:25
The and tags are not always exactly as shown, there will be variations since dynamic content is going to be processed. For example there may be a string such as:
this is some text more text — badcoder, Apr 18 '13 at 10:45
**Don't use regular expressions to parse HTML**. You cannot reliably parse HTML with regular expressions, and you will face sorrow and frustration down the road. As soon as the HTML changes from your expectations, your code will be broken. See http://htmlparsing.com/php for examples of how to properly parse HTML with PHP modules that have already been written, tested and debugged. — Andy Lester, May 09 '13 at 15:09

Potherca · Answer 1 · 2013-05-09T14:56:43.990

I would very strongly advise against using a regular expression for this. Besides being more error prone and less readable, it also does not give you the ability to manipulate the content easily.

You would be better of loading the content into a DomDocument, retrieving all <img> elements and validating whether or not their parents are <a> elements. All you would have to do then is validate whether or not the value of the href attribute ends with the desired extension.

A very crude implementation would look a bit like this:

<?php

$sHtml = <<<HTML
<html>
<body>
    <img src="../images/image.jpg" />
    <a href="www.site.com/document.pdf"><img src="../images/image.jpg" /></a>
    <a href="www.site.com/document.txt"><img src="../images/image.jpg" /></a>
    <p>this is some text <a href="site.com/doc.pdf"> more text</p> 
</body>
</html>
HTML;

$oDoc = new DOMDocument();
$oDoc->loadHTML($sHtml);
$oNodeList = $oDoc->getElementsByTagName('img');

foreach($oNodeList as $t_oNode)
{
    if($t_oNode->parentNode->nodeName === 'a')
    {
        $sLinkValue = $t_oNode->parentNode->getAttribute('href');
        $sExtension = substr($sLinkValue, strrpos($sLinkValue, '.'));

        echo '<li>I am wrapped in an anchor tag '
           . 'and I link to  a ' . $sExtension . ' file '
        ; 
    }
}
?>

I'll leave an exact implementation as an exercise for the reader ;-)

+1 And you could also add `&& preg_match('/\.(pdf|doc)$/i', $t_oNode->parentNode->getAttribute('href'))` to your `if` statement. — MikeM, Apr 18 '13 at 11:28

score 0 · Answer 2 · answered Apr 18 '13 at 11:19

Here is a DOM parse based code that you can use:

$html = <<< EOF
<a href="www.site.com/document.pdf"><img src="../images/image.jpg" /></a>
<img src="../images/image1.jpg" />
<a href="www.site.com/document.txt"><IMG src="../images/image2.jpg" /></a>
<a href="www.site.com/document.doc"><img src="../images/image3.jpg" /></a>
<a href="www.site.com/document1.pdf">My PDF</a>
EOF;
$doc = new DOMDocument();
libxml_use_internal_errors(true);
$doc->loadHTML($html); // loads your html
$nodeList = $doc->getElementsByTagName('a');
for($i=0; $i < $nodeList->length; $i++) {
    $node = $nodeList->item($i);
    $children = $node->childNodes; 
    $hasImage = false;
    foreach ($children as $child) { 
       if ($child->nodeName == 'img') {
          $hasImage = true;
          break;
       }
    }
    if (!$hasImage)
       continue;
    if ($node->hasAttributes())
       foreach ($node->attributes as $attr) {
          $name = $attr->nodeName;
          $value = $attr->nodeValue;
          if ($attr->nodeName == 'href' && 
              preg_match('/\.(doc|pdf)$/i', $attr->nodeValue)) {
                echo $attr->nodeValue . 
                     " - Image is wrapped in a link to a PDF or DOC file\n";
                break;
          }

       }
}

PHP regex to check if image is wrapped with a tag

2 Answers2

Live Demo: http://ideone.com/dwJNAj