CouchbaseBucket::insert() sometimes causes a crash

Program received signal SIGSEGV, Segmentation fault.

0x00007ffff3aca820 in zend_hash_num_elements () from /usr/lib/apache2/modules/libphp5.so

(gdb) where

#0  0x00007ffff3aca820 in zend_hash_num_elements () from /usr/lib/apache2/modules/libphp5.so

#1  0x00007ffff3abadea in _zval_copy_ctor_func () from /usr/lib/apache2/modules/libphp5.so

#2  0x00007ffff3abcda8 in zend_make_printable_zval () from /usr/lib/apache2/modules/libphp5.so

#3  0x00007ffff3ac3841 in zend_is_callable_ex () from /usr/lib/apache2/modules/libphp5.so

#4  0x00007ffff3aad49f in zend_call_function () from /usr/lib/apache2/modules/libphp5.so

#5  0x00007ffff3aae08e in call_user_function_ex () from /usr/lib/apache2/modules/libphp5.so

#6  0x00007ffff3aae0e2 in call_user_function () from /usr/lib/apache2/modules/libphp5.so

#7  0x00007ffff0940a64 in pcbc_bytes_to_zval (zvalue=zvalue@entry=0x7fffffff9ea8, bytes=bytes@entry=0x0, 

    nbytes=nbytes@entry=0, flags=flags@entry=0, datatype=datatype@entry=0 '\000', obj=<optimized out>)

    at /tmp/pear/temp/couchbase/bucket.c:140

#8  0x00007ffff0943140 in make_metadoc_bytes (datatype=0 '\000', flags=0, cas=2188148181853274112, nbytes=0, 

    bytes=0x0, doc=0x555555e65c00, obj=0x555555e5ad38) at /tmp/pear/temp/couchbase/bucket.c:240

#9  store_callback (instance=<optimized out>, cookie=0x555555e70510, operation=<optimized out>, error=LCB_SUCCESS, 

    resp=<optimized out>) at /tmp/pear/temp/couchbase/bucket.c:300

#10 0x00007ffff06fbea0 in ?? () from /usr/lib/libcouchbase.so.2

#11 0x00007ffff07053e2 in ?? () from /usr/lib/libcouchbase.so.2

#12 0x00007ffff070833d in ?? () from /usr/lib/libcouchbase.so.2

#13 0x00007ffff06ed25c in ?? () from /usr/lib/libcouchbase.so.2

#14 0x00007ffff0712c78 in ?? () from /usr/lib/libcouchbase.so.2

#15 0x00007ffff07063fd in lcb_wait () from /usr/lib/libcouchbase.so.2

#16 0x00007ffff09404e1 in pcbc_wait (instance=0x555555b37520) at /tmp/pear/temp/couchbase/bucket.c:394

#17 0x00007ffff0941ad7 in zim_Bucket_insert (ht=<optimized out>, return_value=0x555555e65c00, 

    return_value_ptr=<optimized out>, this_ptr=<optimized out>, return_value_used=<optimized out>)

---Type <return> to continue, or q <return> to quit---

    at /tmp/pear/temp/couchbase/bucket.c:590

#18 0x00007ffff3aabc5b in dtrace_execute_internal () from /usr/lib/apache2/modules/libphp5.so

#19 0x00007ffff3b6bcb5 in ?? () from /usr/lib/apache2/modules/libphp5.so

#20 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#21 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#22 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#23 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#24 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#25 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#26 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#27 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#28 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#29 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#30 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#31 0x00007ffff3aade91 in zend_call_function () from /usr/lib/apache2/modules/libphp5.so

#32 0x00007ffff39e1469 in zif_call_user_func () from /usr/lib/apache2/modules/libphp5.so

#33 0x00007ffff3aabc5b in dtrace_execute_internal () from /usr/lib/apache2/modules/libphp5.so

#34 0x00007ffff3b6bcb5 in ?? () from /usr/lib/apache2/modules/libphp5.so

#35 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#36 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#37 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#38 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#39 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

---Type <return> to continue, or q <return> to quit---

#40 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#41 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#42 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#43 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#44 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#45 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#46 0x00007ffff3aade91 in zend_call_function () from /usr/lib/apache2/modules/libphp5.so

#47 0x00007ffff39e1469 in zif_call_user_func () from /usr/lib/apache2/modules/libphp5.so

#48 0x00007ffff3aabc5b in dtrace_execute_internal () from /usr/lib/apache2/modules/libphp5.so

#49 0x00007ffff3b6bcb5 in ?? () from /usr/lib/apache2/modules/libphp5.so

#50 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#51 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#52 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#53 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#54 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#55 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#56 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#57 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#58 0x00007ffff3b6c300 in ?? () from /usr/lib/apache2/modules/libphp5.so

#59 0x00007ffff3ae59e8 in execute_ex () from /usr/lib/apache2/modules/libphp5.so

#60 0x00007ffff3aabb59 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so

#61 0x00007ffff3abd5e0 in zend_execute_scripts () from /usr/lib/apache2/modules/libphp5.so

#62 0x00007ffff3a5d4c5 in php_execute_script () from /usr/lib/apache2/modules/libphp5.so

---Type <return> to continue, or q <return> to quit---

#63 0x00007ffff3b6d93a in ?? () from /usr/lib/apache2/modules/libphp5.so

#64 0x00005555555aa680 in ap_run_handler ()

#65 0x00005555555aabc9 in ap_invoke_handler ()

#66 0x00005555555bfc2c in ap_internal_redirect ()

#67 0x00007ffff1e6bcfc in ?? () from /usr/lib/apache2/modules/mod_rewrite.so

#68 0x00005555555aa680 in ap_run_handler ()

#69 0x00005555555aabc9 in ap_invoke_handler ()

#70 0x00005555555c016a in ap_process_async_request ()

#71 0x00005555555c0444 in ap_process_request ()

#72 0x00005555555bcf02 in ?? ()

#73 0x00005555555b3cc0 in ap_run_process_connection ()

#74 0x00007ffff448d767 in ?? () from /usr/lib/apache2/modules/mod_mpm_prefork.so

#75 0x00007ffff448d96c in ?? () from /usr/lib/apache2/modules/mod_mpm_prefork.so

#76 0x00007ffff448e6b1 in ?? () from /usr/lib/apache2/modules/mod_mpm_prefork.so

#77 0x000055555559169e in ap_run_mpm ()

#78 0x000055555558ae36 in main ()