Remove <p><br/></p> with DOMxpath or regex?

I use DOMxpath to remove html tags that have empty text node but to keep <br/> tags,

$xpath = new DOMXPath($dom);

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

it works perfectly until I came across another problem,

$content = '<p><br/><br/><br/><br/></p>'; 
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How do remove this kind of messy <br/>and<p>? which means I don't want to allow <br/> alone with <p> but I allow <br/> with proper text like this only,

$content = '<p>first break <br/> second break <br/> the last line</p>'; 

Is that possible?

Or is it better with a regular expression?

I tried something like this,

$nodeList = $xpath->query("//p[text()=<br\s*\/?>\s*]");
    foreach($nodeList as $node) 
    {
        $node->parentNode->removeChild($node);
    }

but it return this error,

Warning: DOMXPath::query() [domxpath.query]: Invalid expression in...

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You can select the unwanted p using XPath:

"//p[count(*)=count(br) and br and normalize-space(.)='']"

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Note to select empty-text nodes shouldn't you better use (?):

"//*[normalize-space(.)='' and not(self::br)]"

This will select any element (but br) whithout text nodes, nodes like:

<p><b/><i/></p>

or

<p> <br/>   <br/>
</p>

included.

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I have almost same situation, i use:

$document->loadHTML(str_replace('<br>', urlencode('<br>'), $string_or_file));

And use urlencode() to change it back for display or inserting to database. Its work for me.

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You could get rid of them all by simply checking to see that the only things within a paragraph are spaces and <br /> tags: preg_replace("\<p\>(\s|\<br\s*\/\>)*\<\/p\>","",$content);

Broken down:

\<p\>    # Match for <p>
(        # Beginning of a group
  \s       # Match a space character
  |        # or...
  \<br\s*\/\> # match a <br /> tag, with any number (including 0) spaces between the <br and />
)*       # Match this whole group (spaces or <br /> tags) 0 or more times.
\<\/p\>  # Match for </p>

I will mention, however, that unless your HTML is well-formatted (one-line, no strange spaces or paragraph classes, etc), you should not use regex to parse this. If it is, this regex should work just fine.