replace single and double quotes

This is the code is use to insert/update text into a database field: $sqledit="update activities set act_extra='$_POST[editextra]', act_extra_fr='$_POST[editextrafr]' where act_id=$_POST[editid]"; Now both $_POST[editextra] and $_POST[editextrafr] can contain single or double quotes. So the query almost always gives me an error. I know I have to replace " with &quot, but I do not know how to replace the single quote so it is shown as a single quote on a webpage when I get it from the database I have been looking into str_replace and preg_replace. But what I really need is a solution that 'replaces' single quotes, double quotes en curly quotes so I tackle all possible problems and the same text as it was inputed in the textarea is shown on the webpage. Thx in advance