Programming PHP, 2nd Edition

Global Variables

To access an internal PHP global variable from a function in your extension, you first have to determine what kind of global variable it is. There are three main types: SAPI globals, executor globals, and extension globals.

SAPI Globals (SG)

SAPI is the Server Abstraction API. It contains any variables related to the web server under which PHP is running. Note that not all SAPI modules are related to web servers—the command-line version of PHP is one example. You can check which SAPI module you are running under by including SAPI.h and then checking sapi_module.name:

    #include <SAPI.h>
    /* then in a function */
    printf("the SAPI module is %s\n", sapi_module.name);

See the sapi_globals_struct in the main/SAPI.h file for a list of available SAPI globals. For example, to access the default_mimetype SAPI global, you would use:

    SG(default_mimetype)

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 { ...