How can I use php to remove tags with empty text node?

For instance,

<div class="box"></div> remove

<a href="#"></a> remove

<p><a href="#"></a></p> remove

<span style="..."></span> remove

But I want to keep the tag with text node like this,

<a href="#">link</a> keep

Edit:

I want to remove something messy like this too,

<p><strong><a href="http://xx.org.uk/dartmoor-arts"></a></strong></p>
<p><strong><a href="http://xx.org.uk/depw"></a></strong></p>
<p><strong><a href="http://xx.org.uk/devon-guild-of-craftsmen"></a></strong></p>

I tested both regex below,

$content = preg_replace('!<(.*?)[^>]*>\s*</\1>!','',$content);
$content = preg_replace('%<(.*?)[^>]*>\\s*</\\1>%', '', $content);

But they leave something like this,

<p><strong></strong></p>
<p><strong></strong></p>
<p><strong></strong></p>

Solution

One way could be:

$dom = new DOMDocument();
$dom->loadHtml(
    '<p><strong><a href="http://xx.org.uk/dartmoor-arts">test</a></strong></p>
    <p><strong><a href="http://xx.org.uk/depw"></a></strong></p>
    <p><strong><a href="http://xx.org.uk/devon-guild-of-craftsmen"></a></strong></p>'
);

$xpath = new DOMXPath($dom);

while(($nodeList = $xpath->query('//*[not(text()) and not(node())]')) && $nodeList->length > 0) {
    foreach ($nodeList as $node) {
        $node->parentNode->removeChild($node);
    }
}

echo $dom->saveHtml();

Probably you'll have to change that a bit for your needs.