';
$regex = '~
( < (?:div|span|a|img|ul|li|blockquote) (?=\s) ) # 1
(?=
(?:
(?:[^>"\']|"[^"]*"|\'[^\']*\')*?
( # 2
\s style \s*=
(?: (?> \s* ([\'"]) \s* (?:(?!\g{-1}) .)* \s* \g{-1} ) #3
| (?> (?!\s*[\'"]) \s* [^\s>]* (?=\s|>) )
)
)
)?
)
\s* (?:".*?"|\'.*?\'|[^>]*?)+
( /?> ) # 4
~xs';
echo preg_replace( $regex, '$1$2$4', $html);
?>