Get-type links won't complete querystring values

Hi everyone. I have certain links for document navigation with a query string where one of the values doesn't fill, so the links don't work. The document is a law navigated with pieces of text taken from an array, where the key is a 12-digit string. The key's first three figures identify each law title, the two next the chapter, the next two the section, etc. The code with the problem is an include that shows a list of sections in each chapter. Each section name in the list is a get-type link to the relevant section contents. Now, the generated URLs show incomplete, e.g. http://localhost/e_ley.php?incl=sptmlaw0&navlinks=navsec&tit=03&ch=02&sec= The variable $r doesn't fill the value for "sec=" so the link won´t work. If I comment out the $r definition the page does show the list but the links don't work. If I remove the // the page just won't show at all (error message). My code so far is this: <?php //PRINT TABLE OF CONTENTS FOR CURRENT CHAPTER $heading="1".$tit.$ch."0000000"; print("<center><b>"); print("$textos[$heading]"); print("</b></center><br>"); $keys= array_keys($textos); foreach($keys as $h): $l=substr($h,3,2); //CHAPTER NUMBER $m=substr($h,1,2); //TITLE NUMBER $n=substr($h,8,4); // $r=substr($h,5,2); //SECTION NUMBER $k=substr($h,7,1); //SECTION HEADING (NUMBER/TITLE/TEXT) $s=substr($h,8,2); //SUBSECTION NUMBER $t=substr($h,10,2); //LETTER ITEM NUMBER if($m==$tit && $l==$ch && $r==$sec && $n=="0000"): if($k=="1"): print("<a href=$PHP_SELF?incl=sptmlaw0&"); print("navlinks=navsec&tit=$m&ch=$l&sec=$r>"); print("$textos[$h]"); print("</a> - "); elseif($k=="2"): print("$textos[$h]<br>"); endif; endif; endforeach; ?> Could anybody help? Thanks in advance Alberto Brea http://estudiobrea.com