How can I remove attributes from an html tag?

Although there are better ways, you could actually strip arguments from html tags with a regular expression:

<?phpfunction stripArgumentFromTags( $htmlString ) {    $regEx = '/([^<]*<\s*[a-z](?:[0-9]|[a-z]{0,9}))(?:(?:\s*[a-z\-]{2,14}\s*=\s*(?:"[^"]*"|\'[^\']*\'))*)(\s*\/?>[^<]*)/i'; // match any start tag    $chunks = preg_split($regEx, $htmlString, -1,  PREG_SPLIT_DELIM_CAPTURE);    $chunkCount = count($chunks);    $strippedString = '';    for ($n = 1; $n < $chunkCount; $n++) {        $strippedString .= $chunks[$n];    }    return $strippedString;}?>

The above could probably be written in less characters, but it does the job (quick and dirty).

Strip attributes using SimpleXML (Standard in PHP5)

<?php// define allowable tags$allowable_tags = '<p><a><img><ul><ol><li><table><thead><tbody><tr><th><td>';// define allowable attributes$allowable_atts = array('href','src','alt');// strip collector$strip_arr = array();// load XHTML with SimpleXML$data_sxml = simplexml_load_string('<root>'. $data_str .'</root>', 'SimpleXMLElement', LIBXML_NOERROR | LIBXML_NOXMLDECL);if ($data_sxml ) {    // loop all elements with an attribute    foreach ($data_sxml->xpath('descendant::*[@*]') as $tag) {        // loop attributes        foreach ($tag->attributes() as $name=>$value) {            // check for allowable attributes            if (!in_array($name, $allowable_atts)) {                // set attribute value to empty string                $tag->attributes()->$name = '';                // collect attribute patterns to be stripped                $strip_arr[$name] = '/ '. $name .'=""/';            }        }    }}// strip unallowed attributes and root tag$data_str = strip_tags(preg_replace($strip_arr,array(''),$data_sxml->asXML()), $allowable_tags);?>

Here is one function that will let you strip all attributes except ones you want:

function stripAttributes($s, $allowedattr = array()) {  if (preg_match_all("/<[^>]*\\s([^>]*)\\/*>/msiU", $s, $res, PREG_SET_ORDER)) {   foreach ($res as $r) {     $tag = $r[0];     $attrs = array();     preg_match_all("/\\s.*=(['\"]).*\\1/msiU", " " . $r[1], $split, PREG_SET_ORDER);     foreach ($split as $spl) {      $attrs[] = $spl[0];     }     $newattrs = array();     foreach ($attrs as $a) {      $tmp = explode("=", $a);      if (trim($a) != "" && (!isset($tmp[1]) || (trim($tmp[0]) != "" && !in_array(strtolower(trim($tmp[0])), $allowedattr)))) {      } else {          $newattrs[] = $a;      }     }     $attrs = implode(" ", $newattrs);     $rpl = str_replace($r[1], $attrs, $tag);     $s = str_replace($tag, $rpl, $s);   }  }  return $s;}

In example it would be:

echo stripAttributes('<p class="one" otherrandomattribute="two">');

or if you eg. want to keep "class" attribute:

echo stripAttributes('<p class="one" otherrandomattribute="two">', array('class'));

Or

Assuming you are to send a message to an inbox and you composed your message with CKEDITOR, you can assign the function as follows and echo it to the $message variable before sending. Note the function with the name stripAttributes() will strip off all html tags that are unnecessary. I tried it and it work fine. i only saw the formatting i added like bold e.t.c.

$message = stripAttributes($_POST['message']);

oryou can echo $message; for preview.