implode() reliably segfaults when passed an empty array; 
the following patch fixes it (for me):

158c158
<       /* convert everything to strings, and calculate length */
---
>     /* check for empty array passed in */
160c160,165
<       while (hash_get_current_data(arr->value.ht, (void **) &tmp) == SUCCESS) {
---
>       if (hash_get_current_data(arr->value.ht, (void **) &tmp) != SUCCESS) {
>               return;
>     }
>
>       /* convert everything to strings, and calculate length */
>     do {
168c173,174
<       }
---
>       } while (hash_get_current_data(arr->value.ht, (void **) &tmp) == SUCCESS);
>