$re = '/<([a-z][a-z0-9]*)(?:[^>]*(\s(src|href|style)=[\'\"][^\'\"]*[\'\"]))?[^>]*?(\/?)>/';
$str = '<title>Hello World</title>
<div fadeout"="" style="margin:0px;" class="xyz">
<img src="abc.jpg" alt="" />
<p style="margin-bottom:10px;">The event is celebrating its 50th anniversary Kö <a style="margin:0px;" href="http://www.germany.travel/">exhibition grounds in Cologne</a>.</p>
<p style="padding:0px;"></p>
<p style="color:black;"><strong>A festival for art lovers</strong></p>
</div>';
$subst = "<$1$2$4>";
$result = preg_replace($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