# Write a Python function to insert a string in the middle of a string.
# Sample function and result :
# insert_sting_middle('[[]]', 'Python') -> [[Python]]
# insert_sting_middle('{{}}', 'PHP') -> {{PHP}}

def insert_string(str, word):
    return str[:2] +word + str[2:]

print(insert_string('[[]]', 'Python'))
print(insert_string('{{}}', 'PHP'))