generate Uniq Transaction Id only Number in Laravel6+

I am posting this question here because i could't find the right solution: I have to make a uniq transaction id which i am generating with the time() + rand() In this function still collision can happen.. My question is is there any better way to perform this within (18 digit) , And What about the rand(10 digits) vs rand(5)+rand(5)

And is there a way to controll the ramsey uuid() length