C :: Function Which Takes A Character Array And Reverses It

Write a c function which takes a string(as a character array, null terminated) and reverses it. it doesn't print the reversed string -- it modifies the given string so that it is reversed.

Code:

void reverse(char array[]) {
char tmp;
int i, j;
for(i=0;i<strlen(array); i++){
for(j=strlen(array)-1;j>=0;j--) {
tmp = array[i];
array[i] = array[j];
array[j] = tmp;
} } }

how come this doesn't work?