在閱讀PHP源碼的時候，會遇到很多諸如：CG()，EG() 這樣的宏，如果不了解這些宏的意義，會給理解源碼造成很大困難。
Zend引擎中有兩個重要的全局變量結構體，就是Zend引擎關閉之前都會存在的變量：
typedef struct _zend_compiler_globals zend_compiler_globals;
typedef struct _zend_executor_globals zend_executor_globals;
/* Compiler */
#ifdef ZTS
# define CG(v) TSRMG(compiler_globals_id, zend_compiler_globals *, v)
int zendparse(void *compiler_globals);
#else
# define CG(v) (compiler_globals.v)
extern ZEND_API struct _zend_compiler_globals compiler_globals;
int zendparse(void);
#endif
/* Executor */
#ifdef ZTS
# define EG(v) TSRMG(executor_globals_id, zend_executor_globals *, v)
#else
# define EG(v) (executor_globals.v)
extern ZEND_API zend_executor_globals executor_globals;
#endif
CG 的含義就是 compiler_globals ，Zend編譯器相關的全局變量；
EG 的含義就是 executor_globals，Zend執行器相關的全局變量；
這兩個結構都包含了很多元素，對理解PHP內核有很重要的意義：
struct _zend_compiler_globals {
zend_stack bp_stack;
zend_stack switch_cond_stack;
zend_stack foreach_copy_stack;
zend_stack object_stack;
zend_stack declare_stack;
zend_class_entry *active_class_entry;
/* variables for list() compilation */
zend_llist list_llist;
zend_llist dimension_llist;
zend_stack list_stack;
zend_stack function_call_stack;
char *compiled_filename;
int zend_lineno;
int comment_start_line;
char *heredoc;
int heredoc_len;
zend_op_array *active_op_array;
HashTable *function_table; /* function symbol table */
HashTable *class_table; /* class table */
HashTable filenames_table;
HashTable *auto_globals;
zend_bool in_compilation;
zend_bool short_tags;
zend_bool asp_tags;
zend_bool allow_call_time_pass_reference;
zend_declarables declarables;
/* For extensions support */
zend_bool extended_info; /* generate extension information for debugger/profiler */
zend_bool handle_op_arrays; /* run op_arrays through op_array handlers */
zend_bool unclean_shutdown;
zend_bool ini_parser_unbuffered_errors;
zend_llist open_files;
long catch_begin;
struct _zend_ini_parser_param *ini_parser_param;
int interactive;
zend_uint start_lineno;
zend_bool increment_lineno;
znode implementing_class;
zend_uint access_type;
char *doc_comment;
zend_uint doc_comment_len;
#ifdef ZEND_MULTIBYTE
zend_encoding **script_encoding_list;
int script_encoding_list_size;
zend_bool detect_unicode;
zend_encoding *internal_encoding;
/* multibyte utility functions */
zend_encoding_detector encoding_detector;
zend_encoding_converter encoding_converter;
zend_encoding_oddlen encoding_oddlen;
#endif /* ZEND_MULTIBYTE */
#ifdef ZTS
HashTable **static_members;
int last_static_member;
#endif
};
struct _zend_executor_globals {
zval **return_value_ptr_ptr;
zval uninitialized_zval;
zval *uninitialized_zval_ptr;
zval error_zval;
zval *error_zval_ptr;
zend_function_state *function_state_ptr;
zend_ptr_stack arg_types_stack;
/* symbol table cache */
HashTable *symtable_cache[SYMTABLE_CACHE_SIZE];
HashTable **symtable_cache_limit;
HashTable **symtable_cache_ptr;
zend_op **opline_ptr;
HashTable *active_symbol_table;
HashTable symbol_table; /* main symbol table */
HashTable included_files; /* files already included */
jmp_buf *bailout;
int error_reporting;
int orig_error_reporting;
int exit_status;
zend_op_array *active_op_array;
HashTable *function_table; /* function symbol table */
HashTable *class_table; /* class table */
HashTable *zend_constants; /* constants table */
zend_class_entry *scope;
zval *This;
long precision;
int ticks_count;
zend_bool in_execution;
HashTable *in_autoload;
zend_function *autoload_func;
zend_bool full_tables_cleanup;
zend_bool ze1_compatibility_mode;
/* for extended information support */
zend_bool no_extensions;
#ifdef ZEND_WIN32
zend_bool timed_out;
#endif
HashTable regular_list;
HashTable persistent_list;
zend_ptr_stack argument_stack;
int user_error_handler_error_reporting;
zval *user_error_handler;
zval *user_exception_handler;
zend_stack user_error_handlers_error_reporting;
zend_ptr_stack user_error_handlers;
zend_ptr_stack user_exception_handlers;
/* timeout support */
int timeout_seconds;
int lambda_count;
HashTable *ini_directives;
HashTable *modified_ini_directives;
zend_objects_store objects_store;
zval *exception;
zend_op *opline_before_exception;
struct _zend_execute_data *current_execute_data;
struct _zend_module_entry *current_module;
zend_property_info std_property_info;
zend_bool active;
void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};
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Ubuntu安裝Nginx php5-fpm MySQL(LNMP環境搭建) http://www.linuxidc.com/Linux/2012-10/72458.htm
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PHP 的下載地址：請點這裡
