php string to array with json encode values

hello i have json encoded dynamic string i want to do split it into my array example;

my string:

$mystring = "u0671u0671u0631u0651u064eu062du0652u0645u064eu0670u0646u0650 u0671u0644u0631u0651u064eu062du0650u064au0645u0650";

my array must be;

Array("u0671","u0671"... ");

thanks for help.

i tried manty times with explode but i didnt.