$a = array('a','b','c','d','k','o','i','s','h','t','u','z','y','w','v','m','n','e','A','B','C','D','K','O','I','S','H',U','M','S','T','E','J','L','P','R','W');
$rand = rand(00000, 99999);
$o = $a[rand(0,10)];
$o1 = $a[rand(0,15)];
$o2 = $a[rand(0,25)];
$o3 = $a[rand(0,37)];
$oo = $o.$o1.$rand.$o2.$o3;
echo ''.$oo.'';
Генерация случайного набора символов