The main concern when you have a text in a cell is for long words that drags the cell margins. This function will break words in a text that have more then $nr characters using the "-" char.

<?php
function processtext($text,$nr=10)
    {
        $mytext=explode(" ",trim($text));
        $newtext=array();
        foreach($mytext as $k=>$txt)
        {
            if (strlen($txt)>$nr)
            {
                $txt=wordwrap($txt, $nr, "-", 1);
            }
            $newtext[]=$txt;
        }
        return implode(" ",$newtext);
    }
?>