PHP内核中重要的两个全局变量

在阅读PHP源码的时候，会遇到很多诸如：CG()，EG() 这样的宏，如果不了解这些宏的意义，会给理解源码造成很大困难。

Zend引擎中有两个重要的全局变量结构体，就是Zend引擎关闭之前都会存在的变量：

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 的含义就是 compiler_globals ，Zend编译器相关的全局变量；

EG 的含义就是 executor_globals，Zend执行器相关的全局变量；

这两个结构都包含了很多元素，对理解PHP内核有很重要的意义：

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];};