这里阅读的php版本为PHP-7.1.0 RC3，阅读代码的平台为linux

CG

CG是从全局的compiler_global中获取属性值，里面存储的就是编译过程使用到的全局变量。

struct _zend_compiler_globals {
    zend_stack loop_var_stack;

    zend_class_entry *active_class_entry;

    zend_string *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 unclean_shutdown;

    zend_bool ini_parser_unbuffered_errors;

    zend_llist open_files;

    struct _zend_ini_parser_param *ini_parser_param;

    uint32_t start_lineno; // 执行文件开始执行的行号
    zend_bool increment_lineno;

    zend_string *doc_comment;
    uint32_t extra_fn_flags;

    uint32_t compiler_options; /* set of ZEND_COMPILE_* constants */

    HashTable const_filenames;

    zend_oparray_context context;
    zend_file_context file_context;

    zend_arena *arena;

    zend_string *empty_string;
    zend_string *one_char_string[256];
    zend_string **known_strings;
    uint32_t    known_strings_count;

    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;

    zend_ast *ast;
    zend_arena *ast_arena;

    zend_stack delayed_oplines_stack;

#ifdef ZTS
    zval **static_members_table;
    int last_static_member;
#endif
};

SG

SG是从全局的sapi_global中获取属性值

// TODO：更新
typedef struct _sapi_globals_struct {
    void *server_context;
    sapi_request_info request_info; // 请求信息
    sapi_headers_struct sapi_headers;
    int64_t read_post_bytes;
    unsigned char post_read;
    unsigned char headers_sent;
    zend_stat_t global_stat;
    char *default_mimetype;
    char *default_charset;
    HashTable *rfc1867_uploaded_files;
    zend_long post_max_size;
    int options;
    zend_bool sapi_started;
    double global_request_time;
    HashTable known_post_content_types;
    zval callback_func;
    zend_fcall_info_cache fci_cache;
} sapi_globals_struct;

EG

EG是从executor_globals中获取变量

// TODO: 更新
struct _zend_executor_globals {
    zval uninitialized_zval;
    zval error_zval;

    /* symbol table cache */
    zend_array *symtable_cache[SYMTABLE_CACHE_SIZE];
    zend_array **symtable_cache_limit;
    zend_array **symtable_cache_ptr;

    zend_array symbol_table;        /* main symbol table */

    HashTable included_files;    /* files already included */

    JMP_BUF *bailout;

    int error_reporting;
    int exit_status;

    HashTable *function_table;    /* function symbol table */
    HashTable *class_table;        /* class table */
    HashTable *zend_constants;    /* constants table */

    zval          *vm_stack_top;
    zval          *vm_stack_end;
    zend_vm_stack  vm_stack;

    struct _zend_execute_data *current_execute_data;
    zend_class_entry *fake_scope; /* used to avoid checks accessing properties */

    zend_long precision;

    int ticks_count;

    HashTable *in_autoload;
    zend_function *autoload_func;
    zend_bool full_tables_cleanup;

    /* for extended information support */
    zend_bool no_extensions;

    zend_bool vm_interrupt;
    zend_bool timed_out;
    zend_long hard_timeout;

#ifdef ZEND_WIN32
    OSVERSIONINFOEX windows_version_info;
#endif

    HashTable regular_list;
    HashTable persistent_list;

    int user_error_handler_error_reporting;
    zval user_error_handler;
    zval user_exception_handler;
    zend_stack user_error_handlers_error_reporting;
    zend_stack user_error_handlers;
    zend_stack user_exception_handlers;

    zend_error_handling_t  error_handling;
    zend_class_entry      *exception_class;

    /* timeout support */
    zend_long timeout_seconds;

    int lambda_count;

    HashTable *ini_directives;
    HashTable *modified_ini_directives;
    zend_ini_entry *error_reporting_ini_entry;

    zend_objects_store objects_store;
    zend_object *exception, *prev_exception;
    const zend_op *opline_before_exception;
    zend_op exception_op[3];

    struct _zend_module_entry *current_module;

    zend_bool active;
    zend_bool valid_symbol_table;

    zend_long assertions;

    uint32_t           ht_iterators_count;     /* number of allocatd slots */
    uint32_t           ht_iterators_used;      /* number of used slots */
    HashTableIterator *ht_iterators;
    HashTableIterator  ht_iterators_slots[16];

    void *saved_fpu_cw_ptr;
#if XPFPA_HAVE_CW
    XPFPA_CW_DATATYPE saved_fpu_cw;
#endif

    zend_function trampoline;
    zend_op       call_trampoline_op;

    void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};