In PHP, how to remove wrapping paragraph, but only if it's the only paragraph

How to remove the (in this case, useless) wrapping paragraph in cases like this:

<p>Only paragraph</p>

But to keep the string as it is when there is more than one paragraph involved:

<p>Paragraph 1</p>
<p>Paragraph 2</p>

preg_replace would probably do the trick in here but only if you can handle regexps.. :/

Here is one way, 2 test cases, $a and $b

$a = '<p>Only paragraph</p>';

$b = '<p>Only paragraph</p>
      <p>Only paragraph</p>
      <p>Only paragraph</p>';

// change the values to $a and then $b
if( count( explode('<p>', $a) ) == 2 ){
  $c = preg_replace('#</?p>#', '', $a);
}

if( isset( $c)) {
    var_dump( $c );
}
// 'Only paragraph'

You might need to add a trim() first as well.

Does not cater for malformed input eg

<p>para1 </p> para 2</p>