If "LLL" and "LLNNNN" are the 'standard' format, then you can use strlen to check the string length. If string length is 3, then its usertype1. If its 6, the usertype is 2. Well, this is the simplest way. But if you want to thoroughly check, you can explode the variable into an array, (so the array will be $arr[0]="L"; $arr[1]="L"; $arr[2]="L"; and so on ). Then foreach array element, check if its a character or a number. If the character count is 3 and number count is 0, then the usertype is 1. If character count is 2 and number count is 4, then its usertype2.
It really depends on what logic you want to use in your script.