When a function is defined to return an array its return_value variable is already appropriately initialized. All you have to do is to add the acutal array elements to return_value.

The Zend API provides a rich set of functions for adding various data types as array elements, supporting numerical, associative and automatic indexes. 

// adding an integer element
add_assoc_long(return_value, "index", 42); // like $array["index"] = 42;
add_index_long(return_value, 23, 42);      // like $array[23] = 42;
add_next_index_long(return_value, 42);     // like $array[] = 42;

// adding a string element (string is copied)
add_assoc_string(return_value, "foo", "bar", 1); // like $array["foo"] = "bar"
add_assoc_stringl(return_value, "foo", "bar", 3, 1);  // the same binary safe including length

// adding a string element previously allocated using emalloc
add_assoc_string(return_value, "foo", "bar", 0); // no need to copy as memory is already managed

// general form of adding a zval 
add_assoc_zval(return_value, "foobar", zval_ptr);