$sansas = rand(1,5);
if ($sansas == 1) { echo "<img src="headeris1.gif" alt="">"; }
elseif ($sansas == 2) { echo "<img src="headeris2.gif" alt="">"; }
elseif ($sansas == 3) { echo "<img src="headeris3.gif" alt="">"; }
elseif ($sansas == 4) { echo "<img src="headeris4.gif" alt="">"; }
elseif ($sansas == 5) { echo "<img src="headeris5.gif" alt="">"; }