FYI only:
Maybe I am being pedantic :-) but you actually should write:
<textarea cols="40" rows="3" name="blah" readonly="readonly">
$content
</textarea>
Empty attributes are not allowed by the HTML and XHTML recommendations.
Bryan´s code will work but that´s because browsers being forgiving. Next browser maybe will follow the HTML and/or XHTML recommendations and you will then get an error. NOTE! Some browsers do not recognize the readonly-attribute hence making editing fully possible.