Description:
------------
If you can't guess from the backtrace - I'll try and get the reproduce code working
- This is PHP4.3.4RC3 + xdebug 1.3.0rc1
- looks like an overload issue.

Regards
Alan

Reproduce code:
---------------
 

Actual result:
--------------
0x4055f071 in add_stack_frame (zdata=0xbfff61b0, op_array=0x81829b4, type=0)
---Type <return> to continue, or q <return> to quit---\
    at /usr/src/php/xdebug-1.3.0rc1/xdebug.c:595
595                                     (strcmp(tmpf->common.function_name, "call_user_func") == 0) ||
(gdb) bt full
#0  0x4055f071 in add_stack_frame (zdata=0xbfff61b0, op_array=0x81829b4,
    type=0) at /usr/src/php/xdebug-1.3.0rc1/xdebug.c:595
        tmpf = (zend_function *) 0x0
        tmp = (struct function_stack_entry *) 0x823e000
        cur_opcode = (zend_op *) 0x0
        param = (zval **) 0x0
        arg_count = 3
        i = 0
        p = (void **) 0x4056d742
        arg_count = 0
#1  0x4055f6be in xdebug_execute (op_array=0x81829b4)
    at /usr/src/php/xdebug-1.3.0rc1/xdebug.c:765
        edata = (zend_execute_data *) 0xbfff61b0
        fse = (struct function_stack_entry *) 0xbfff6830
#2  0x40407127 in call_user_function_ex (function_table=0xbfff6288,
    object_pp=0xbfff625c, function_name=0xbfff6320, retval_ptr_ptr=0xbfff6260,
    param_count=3, params=0xbfff6300, no_separation=0, symbol_table=0x0)
    at /usr/src/php/php-4.3.4RC3/Zend/zend_execute_API.c:567
        param = (zval *) 0xbfff6830
        i = 3
        original_return_value = (zval **) 0xbfff7390
        calling_symbol_table = (HashTable *) 0x823bf34
        original_function_state_ptr = (zend_function_state *) 0xbfff6834
---Type <return> to continue, or q <return> to quit---
        original_op_array = (zend_op_array *) 0x81d7c44
        original_opline_ptr = (zend_op **) 0xbfff6830
        orig_free_op1 = 0
        orig_free_op2 = 0
    zval *)) 0x4040a940 <boolean_not_function>
        orig_binary_op = (int (*)(zval *, zval *,
    zval *)) 0x4040b760 <concat_function>
        function_name_copy = {value = {lval = 136565372,
    dval = 1.2799447004508364e-313, str = {val = 0x823d27c "__call", len = 6},
    ht = 0x823d27c, obj = {ce = 0x823d27c, properties = 0x6}},
  type = 3 '\003', is_ref = 0 '\0', refcount = 1}
        execute_data = {opline = 0x0, function_state = {
    function_symbol_table = 0x34, function = 0x81829b4, reserved = {
      0x404620d0, 0x823df04, 0x0, 0xbfff61e8}}, fbc = 0x0, ce = 0x0, object = {
    ptr = 0x823d83c}, Ts = 0x0, original_in_execution = 208 '?',
  op_array = 0x0, prev_execute_data = 0xbfff6830}
#3  0x403526bc in overload_call_method (ht=0, return_value=0x823d604,
    this_ptr=0x823d83c, return_value_used=1, property_reference=0x4056d742)
    at /usr/src/php/php-4.3.4RC3/ext/overload/overload.c:566
        handler_args = {0xbfff626c, 0xbfff6268, 0xbfff6264}
        result_ptr = (zval *) 0xbfff62f0
        temp_ce = {type = 2 '\002', name = 0x80fccc4 "dataobjects_staff",
---Type <return> to continue, or q <return> to quit---
  name_length = 17, parent = 0x8205798, refcount = 0x80fd164,
  constants_updated = 1 '\001', function_table = {nTableSize = 64,
    nTableMask = 63, nNumOfElements = 52, nNextFreeElement = 0,
    pInternalPointer = 0x81889cc, pListHead = 0x81889cc,
    pListTail = 0x8182d64, arBuckets = 0x81820f4,
    pDestructor = 0x40408730 <destroy_zend_function>, persistent = 0 '\0',
    nApplyCount = 0 '\0', bApplyProtection = 1 '\001'}, default_properties = {
    nTableSize = 64, nTableMask = 63, nNumOfElements = 37,
    nNextFreeElement = 0, pInternalPointer = 0x8167784, pListHead = 0x8167784,
    pListTail = 0x8180f54, arBuckets = 0x8180e04,
    pDestructor = 0x40406700 <_zval_ptr_dtor>, persistent = 0 '\0',
    nApplyCount = 0 '\0', bApplyProtection = 1 '\001'},
  builtin_functions = 0x0, handle_function_call = 0, handle_property_get = 0,
  handle_property_set = 0}
        i = -1073782168
        arg_array = (zval *) 0x823d5e4
        result = {value = {lval = 1076705888, dval = 1.8804525693524069e-269,
    str = {val = 0x402d3a60 "", len = 136568416}, ht = 0x402d3a60, obj = {
      ce = 0x402d3a60, properties = 0x823de60}}, type = 0 '\0',
  is_ref = 1 '\001', refcount = 2}
        orig_ce = (zend_class_entry *) 0x8182e40
        args = (zval ***) 0x823d314
        retval = (zval *) 0x0
---Type <return> to continue, or q <return> to quit---b
..;.......and on and on...