Remove style attribute from HTML tags

I'm not too good with regular expressions, but with PHP I'm wanting to remove the style attribute from HTML tags in a string that's coming back from TinyMCE.

So change <p style="...">Text</p> to just vanilla <p>Test</p>.

How would I achieve this with something like the preg_replace() function?

The pragmatic regex (<[^>]+) style=".*?" will solve this problem in all reasonable cases. The part of the match that is not the first captured group should be removed, like this:

$output = preg_replace('/(<[^>]+) style=".*?"/i', '$1', $input);

Match a < followed by one or more "not >" until we come to space and the style="..." part. The /i makes it work even with STYLE="...". Replace this match with $1, which is the captured group. It will leave the tag as is, if the tag doesn't include style="...".

Something like this should work (untested code warning):

<?php

$html = '<p style="asd">qwe</p><br /><p class="qwe">qweqweqwe</p>';

$domd = new DOMDocument();
libxml_use_internal_errors(true);
$domd->loadHTML($html);
libxml_use_internal_errors(false);

$domx = new DOMXPath($domd);
$items = $domx->query("//p[@style]");

foreach($items as $item) {
  $item->removeAttribute("style");
}

echo $domd->saveHTML();

I commented on @Mayerln 's function. It does work but DOMDocument really stuffs with encoding. Here's my simplehtmldom version

function stripAttributes($html,$attribs) {
    $dom = new simple_html_dom();
    $dom->load($html);
    foreach($attribs as $attrib)
        foreach($dom->find("*[$attrib]") as $e)
            $e->$attrib = null; 
    $dom->load($dom->save());
    return $dom->save();
}

Here you go:

<?php

$html = '<p style="border: 1px solid red;">Test</p>';
echo preg_replace('/<p style="(.+?)">(.+?)<\/p>/i', "<p>$2</p>", $html);

?>

By the way, as pointed out by others, regex are not suggested for this.

I use this:

function strip_word_html($text, $allowed_tags = '<a><ul><li><b><i><sup><sub><em><strong><u><br><br/><br /><p><h2><h3><h4><h5><h6>')
{
	mb_regex_encoding('UTF-8');
	//replace MS special characters first
	$search = array('/&lsquo;/u', '/&rsquo;/u', '/&ldquo;/u', '/&rdquo;/u', '/&mdash;/u');
	$replace = array('\'', '\'', '"', '"', '-');
	$text = preg_replace($search, $replace, $text);
	//make sure _all_ html entities are converted to the plain ascii equivalents - it appears
	//in some MS headers, some html entities are encoded and some aren't
	//$text = html_entity_decode($text, ENT_QUOTES, 'UTF-8');
	//try to strip out any C style comments first, since these, embedded in html comments, seem to
	//prevent strip_tags from removing html comments (MS Word introduced combination)
	if(mb_stripos($text, '/*') !== FALSE){
		$text = mb_eregi_replace('#/\*.*?\*/#s', '', $text, 'm');
	}
	//introduce a space into any arithmetic expressions that could be caught by strip_tags so that they won't be
	//'<1' becomes '< 1'(note: somewhat application specific)
	$text = preg_replace(array('/<([0-9]+)/'), array('< $1'), $text);
	$text = strip_tags($text, $allowed_tags);
	//eliminate extraneous whitespace from start and end of line, or anywhere there are two or more spaces, convert it to one
	$text = preg_replace(array('/^\s\s+/', '/\s\s+$/', '/\s\s+/u'), array('', '', ' '), $text);
	//strip out inline css and simplify style tags
	$search = array('#<(strong|b)[^>]*>(.*?)</(strong|b)>#isu', '#<(em|i)[^>]*>(.*?)</(em|i)>#isu', '#<u[^>]*>(.*?)</u>#isu');
	$replace = array('<b>$2</b>', '<i>$2</i>', '<u>$1</u>');
	$text = preg_replace($search, $replace, $text);
	//on some of the ?newer MS Word exports, where you get conditionals of the form 'if gte mso 9', etc., it appears
	//that whatever is in one of the html comments prevents strip_tags from eradicating the html comment that contains
	//some MS Style Definitions - this last bit gets rid of any leftover comments */
	$num_matches = preg_match_all("/\<!--/u", $text, $matches);
	if($num_matches){
		$text = preg_replace('/\<!--(.)*--\>/isu', '', $text);
	}
	$text = preg_replace('/(<[^>]+) style=".*?"/i', '$1', $text);
return $text;
}

I'm using such thing to clean-up the style='...' section out of tags with keeping of other attributes at the moment.

$output = preg_replace('/<([^>]+)(\sstyle=(?P<stq>["\'])(.*)\k<stq>)([^<]*)>/iUs', '<$1$5>', $input);

In addition to Lorenzo Marcon's answer:

Using preg_replace to select everything except style attribute:

$html = preg_replace('/(<p.+?)style=".+?"(>.+?)/i', "$1$2", $html);

$html = preg_replace('/\sstyle=("|\').*?("|\')/i', '', $html);

For replacing all style="" with blank.

You could handle it client side, the easiest would be with jQuery. Something like:

$("#tinyMce p").removeAttr("style");