Programming PHP

Some elements of the SAPI globals structure are themselves structures with fields.
For example, to access the request_uri, use:
SG(request_info).request_uri
Executor Globals (EG)
These are runtime globals defined internally by the Zend executor. The most common
EG variables are symbol_table (which holds the main symbol table) and active_
symbol_table (which holds the currently visible symbols).
For example, to see if the user-space $foo variable has been set, you could do:
zval **tmp;
if(zend_hash_find(&EG(symbol_table), "foo", sizeof("foo"),
(void **)&tmp) == SUCCESS) {
RETURN_STRINGL(Z_STRVAL_PP(tmp), Z_STRLEN_PP(tmp));
} else {
RETURN_FALSE;
}
Internal Extension Globals
Sometimes you need extensionwide global C variables. Since an extension has to be
thread-safe, global variables are a problem. You can solve this problem by creating a
struct—each would-be global variable becomes a field in the struct. When compiled
as a thread-safe extension, macros take care of passing this struct around. When
compiled as a non-thread-safe extension, the struct is a true global struct that is
accessed directly. This way, the non-thread-safe builds do not suffer the slight performance
penalty of passing around this global struct.
These macros look something like this for a thread-safe build:
#define TSRMLS_FETCH( ) void ***tsrm_ls = (void ***) ts_resource_ex(0, NULL)
#define TSRMG(id,type,el) (((type) (*((void ***) \
tsrm_ls))[TSRM_UNSHUFFLE_RSRC_ID(id)])->el)
#define TSRMLS_D void ***tsrm_ls
#define TSRMLS_DC , TSRMLS_D
#define TSRMLS_C tsrm_ls
#define TSRMLS_CC , TSRMLS_C
For the non-thread-safe build, they don’t do anything and are simply defined as:
#define TSRMLS_FETCH( )
#define TSRMLS_D void
#define TSRMLS_DC
#define TSRMLS_C
#define TSRMLS_CC
#endif /* ZTS */
So, to create extensionwide global variables, you first need to create a struct in which
to store them, along with the thread-safe and non-thread-safe access macros.
344 | Chapter 14: Extending PHP
This is the Title of the Book, eMatter Edition
Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.