$re = '/<([^>]*)>[^><]*<\/\s*\1\s*>|<(\w+)\s+[^>]*>[^><]*<\/\s*\2\s*>/m';
$str = '<div id="MyDiv">div,
<strong>
<span>span2, </span> <-- This is to delete
<em> Some text for em
<div> Some text for div </div> <-- This is to delete
<p><b>b, <span id="MySpan"> Some text for span ...
<b style="z-index:1;"> text ... </ b >';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php