I had exactly the same problem last week and thought about it for quite a while.
It seems, that associative arrays can’t be serialized or copied. There’s a good Bash FAQ entry to associative arrays which explains them in detail. The last section gave me the following idea which works for me:
function print_array {
# eval string into a new associative array
eval "declare -A func_assoc_array="${1#*=}
# proof that array was successfully created
declare -p func_assoc_array
}
# declare an associative array
declare -A assoc_array=(["key1"]="value1" ["key2"]="value2")
# show associative array definition
declare -p assoc_array
# pass associative array in string form to function
print_array "$(declare -p assoc_array)"