$banners = array('txt1','txt2','txt2','txt4','txt6=5',);
$cc = count($banners) ;
$cl = $cc-1;
do {
$rand = rand(0,$cl);
$rand2 = rand(0,$cl);
$rand3 = rand(0,$cl);
} while ($rand != $rand2 or $rand2!=$rand3 or $rand!=$rand3);
echo " $banners[$rand];
$banners[$rand2];
$banners[$rand3];";