If you get the error:
error:0D11A086:asn1 encoding routines:ASN1_mbstring_copy:string too short
then look at your key:value pairs in the $dn (distinguished name) array.
If you have one value (like "organizationalUnitName" = "") set to an empty string, it will throw the above error.
Fix the error by either eliminating that array element from $dn completely, or using a space " " instead of an empty string.