[office politics]

if a = 1 it displays a

then it evaluates the second if else

so since a is not 0, it echo's b

to prevent b from being displayed, put a else after echo a.

<? if ($a == 1) 
	echo "a";
          else {
	if ($a == 0) 
	      echo "";
                else 
    	     echo "b";
	}
	?>