generate 14 digit random number in php

heres my code

while($x <= $num) {
$code = rand(1,666666).rand(2,88888888);

$INC = qry_run("Insert into ms_code2 (code) Values(".$code.")");

$x++;
} 

the main problem is when this loop work sometimes it generate 14 number sometimes 10 and sometimes 12