深入PHP内核之全局变量

在阅读PHP源码的时候，会遇到很多诸如：CG()，EG() ，PG()，FG()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

EG()、这个宏可以用来访问符号表，函数，资源信息和常量

CG() 用来访问核心全局变量

PG() PHP全局变量。我们知道php.ini会映射一个或者多个PHP全局结构。举几个使用这个宏的例子：PG(register_globals), PG(safe_mode), PG(memory_limit)

FG() 文件全局变量。大多数文件I/O或相关的全局变量的数据流都塞进标准扩展出口结构。

申明 Zend/zend_globals_macros.h

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

 结构体中的具体定义 Zend/zend_globals.h

/* Define ZTS if you want a thread-safe Zend */
/*#undef ZTS*/
 
#ifdef ZTS
 
BEGIN_EXTERN_C()
ZEND_API extern int compiler_globals_id;
ZEND_API extern int executor_globals_id;
END_EXTERN_C()
 
#endif

 struct _zend_compiler_globals

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;
 
        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 parse_error;
        zend_bool in_compilation;
        zend_bool short_tags;
        zend_bool asp_tags;
 
        zend_declarables declarables;
 
        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;
 
        zend_uint compiler_options; /* set of ZEND_COMPILE_* constants */
 
        zval      *current_namespace;
        HashTable *current_import;
        HashTable *current_import_function;
        HashTable *current_import_const;
        zend_bool  in_namespace;
        zend_bool  has_bracketed_namespaces;
 
        HashTable const_filenames;
 
        zend_compiler_context context;
        zend_stack context_stack;
 
        /* interned strings */
        char *interned_strings_start;
        char *interned_strings_end;
        char *interned_strings_top;
        char *interned_strings_snapshot_top;
#ifndef ZTS
        char *interned_empty_string;
#endif
 
        HashTable interned_strings;
 
        const zend_encoding **script_encoding_list;
        size_t script_encoding_list_size;
        zend_bool multibyte;
        zend_bool detect_unicode;
        zend_bool encoding_declared;
 
#ifdef ZTS
        zval ***static_members_table;
        int last_static_member;
#endif
};

struct _zend_executor_globals

struct _zend_executor_globals {
        zval **return_value_ptr_ptr;
 
        zval uninitialized_zval;
        zval *uninitialized_zval_ptr;
 
        zval error_zval;
        zval *error_zval_ptr;
 
        /* 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;
        zend_class_entry *called_scope; /* Scope of the calling class */
 
        zval *This;
 
        long precision;
 
        int ticks_count;
 
        zend_bool in_execution;
        HashTable *in_autoload;
        zend_function *autoload_func;
        zend_bool full_tables_cleanup;
 
        /* for extended information support */
        zend_bool no_extensions;
 
#ifdef ZEND_WIN32
        zend_bool timed_out;
        OSVERSIONINFOEX windows_version_info;
#endif
 
        HashTable regular_list;
        HashTable persistent_list;
 
        zend_vm_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;
 
        zend_error_handling_t  error_handling;
        zend_class_entry      *exception_class;
 
        /* timeout support */
        int timeout_seconds;
 
        int lambda_count;
 
        HashTable *ini_directives;
        HashTable *modified_ini_directives;
        zend_ini_entry *error_reporting_ini_entry;
 
        zend_objects_store objects_store;
        zval *exception, *prev_exception;
        zend_op *opline_before_exception;
        zend_op exception_op[3];
 
        struct _zend_execute_data *current_execute_data;
 
        struct _zend_module_entry *current_module;
 
        zend_property_info std_property_info;
 
        zend_bool active;
 
        zend_op *start_op;
 
        void *saved_fpu_cw_ptr;
#if XPFPA_HAVE_CW
        XPFPA_CW_DATATYPE saved_fpu_cw;
#endif
 
        void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};

一般EG用的比较多