Changes to PHP Internals
  
   - 
    
     Extensions cannot override zend_execute() any more and
     should override zend_execute_ex() instead.
     EG(current_execute_data) is already initialized in
     zend_execute_ex(), so for compatibility extensions may
     need to use
     EG(current_execute_data)->prev_execute_data instead.
    
   
- 
    
     Removed EG(arg_types_stack),
     EX(fbc), EX(called_scope) and
     EX(current_object).
    
   
- 
    
     Added op_array->nested_calls, which is calculated
     at compile time.
    
   
- 
    
     Added EX(call_slots), which is an array to store
     information about syntaticaly nested calls (e.g.
     foo(bar())) and is preallocated together with
     execute_data.
    
   
- 
    
     Added EX(call), which is a pointer to a current
     calling function, and is an element of EX(call_slots).
    
   
- 
    
     Opcodes
     INIT_METHOD_CALL,
     ZEND_INIT_STATIC_METHOD_CALL,
     ZEND_INIT_FCALL_BY_NAME
     and
     ZEND_INIT_NS_FCALL_BY_NAME
     use result.num as an index in
     EX(call_slots).
    
   
- 
    
     Opcode ZEND_NEW uses
     extended_value as an index in
     EX(call_slots).
    
   
- 
    
     Opcodes ZEND_DO_FCALL
     and
     ZEND_DO_FCALL_BY_NAME
     use op2.num as an index in
     EX(call_slots).
    
   
- 
    
     Added op_array->used_stack, which is calculated at
     compile time; the corresponding stack space is preallocated together with
     execute_data. As a result, the ZEND_SEND* and
     ZEND_DO_FCALL* opcodes no longer need to check for stack overflow.
    
   
- 
    
     Removed execute_data->Ts field. The VM temporary
     variables are always allocated immediately before the
     execute_data structure, and are now accessed by their
     offset from the execute_data base pointer instead of
     via execute_data->Ts.  The compiler stores new
     offsets in op_array->opcodes[*].op?.num.  The
     EX_TMP_VAR() and EX_TMP_VAR_NUM()
     macros can be used to access temporary variables by offset or number. You
     can convert the number to an offset using EX_TMP_VAR_NUM(0,
     num) or offset to number using
     (EX_TMP_VAR_NUM(0,0)-EX_TMP_VAR(0,offset)).
    
   
- 
    
     Removed the execute_data->CVs field. The VM
     compiled variables are always allocated immediately after the
     execute_data structure, and are now accessed by the
     offset from the execute_data base pointer instead of
     via execute_data->CVs. You can use the
     EX_CV_NUM() macro to access compiled variables by
     number.