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Declaration of the Zend Module Block

This block is stored in the structure zend_module_entry and contains all necessary information to describe the contents of this module to Zend. You can see the internal definition of this module in Example 31-2.

Example 31-2. Internal declaration of zend_module_entry.

typedef struct _zend_module_entry zend_module_entry;
     
    struct _zend_module_entry {
    unsigned short size;
    unsigned int zend_api;
    unsigned char zend_debug;
    unsigned char zts;
    char *name;
    zend_function_entry *functions;
    int (*module_startup_func)(INIT_FUNC_ARGS);
    int (*module_shutdown_func)(SHUTDOWN_FUNC_ARGS);
    int (*request_startup_func)(INIT_FUNC_ARGS);
    int (*request_shutdown_func)(SHUTDOWN_FUNC_ARGS);
    void (*info_func)(ZEND_MODULE_INFO_FUNC_ARGS);
    char *version;

[ Rest of the structure is not interesting here ]

 };

EntryDescription
size, zend_api, zend_debug and zts Usually filled with the "STANDARD_MODULE_HEADER", which fills these four members with the size of the whole zend_module_entry, the ZEND_MODULE_API_NO, whether it is a debug build or normal build (ZEND_DEBUG) and if ZTS is enabled (USING_ZTS).
name Contains the module name (for example, "File functions", "Socket functions", "Crypt", etc.). This name will show up in phpinfo(), in the section "Additional Modules."
functions Points to the Zend function block, discussed in the preceding section.
module_startup_func This function is called once upon module initialization and can be used to do one-time initialization steps (such as initial memory allocation, etc.). To indicate a failure during initialization, return FAILURE; otherwise, SUCCESS. To mark this field as unused, use NULL. To declare a function, use the macro ZEND_MINIT.
module_shutdown_func This function is called once upon module shutdown and can be used to do one-time deinitialization steps (such as memory deallocation). This is the counterpart to module_startup_func(). To indicate a failure during deinitialization, return FAILURE; otherwise, SUCCESS. To mark this field as unused, use NULL. To declare a function, use the macro ZEND_MSHUTDOWN.
request_startup_func This function is called once upon every page request and can be used to do one-time initialization steps that are required to process a request. To indicate a failure here, return FAILURE; otherwise, SUCCESS. Note: As dynamic loadable modules are loaded only on page requests, the request startup function is called right after the module startup function (both initialization events happen at the same time). To mark this field as unused, use NULL. To declare a function, use the macro ZEND_RINIT.
request_shutdown_func This function is called once after every page request and works as counterpart to request_startup_func(). To indicate a failure here, return FAILURE; otherwise, SUCCESS. Note: As dynamic loadable modules are loaded only on page requests, the request shutdown function is immediately followed by a call to the module shutdown handler (both deinitialization events happen at the same time). To mark this field as unused, use NULL. To declare a function, use the macro ZEND_RSHUTDOWN.
info_func When phpinfo() is called in a script, Zend cycles through all loaded modules and calls this function. Every module then has the chance to print its own "footprint" into the output page. Generally this is used to dump environmental or statistical information. To mark this field as unused, use NULL. To declare a function, use the macro ZEND_MINFO.
version The version of the module. You can use NO_VERSION_YET if you don't want to give the module a version number yet, but we really recommend that you add a version string here. Such a version string can look like this (in chronological order): "2.5-dev", "2.5RC1", "2.5" or "2.5pl3".
Remaining structure elements These are used internally and can be prefilled by using the macro STANDARD_MODULE_PROPERTIES_EX. You should not assign any values to them. Use STANDARD_MODULE_PROPERTIES_EX only if you use global startup and shutdown functions; otherwise, use STANDARD_MODULE_PROPERTIES directly.

In our example, this structure is implemented as follows:
zend_module_entry firstmod_module_entry =
{
    STANDARD_MODULE_HEADER,
    "First Module",
    firstmod_functions,
    NULL, NULL, NULL, NULL, NULL,
    NO_VERSION_YET,
    STANDARD_MODULE_PROPERTIES,
 };
This is basically the easiest and most minimal set of values you could ever use. The module name is set to First Module, then the function list is referenced, after which all startup and shutdown functions are marked as being unused.

For reference purposes, you can find a list of the macros involved in declared startup and shutdown functions in Table 31-3. These are not used in our basic example yet, but will be demonstrated later on. You should make use of these macros to declare your startup and shutdown functions, as these require special arguments to be passed (INIT_FUNC_ARGS and SHUTDOWN_FUNC_ARGS), which are automatically included into the function declaration when using the predefined macros. If you declare your functions manually and the PHP developers decide that a change in the argument list is necessary, you'll have to change your module sources to remain compatible.

Table 31-3. Macros to Declare Startup and Shutdown Functions

MacroDescription
ZEND_MINIT(module) Declares a function for module startup. The generated name will be zend_minit_<module> (for example, zend_minit_first_module). Use in conjunction with ZEND_MINIT_FUNCTION.
ZEND_MSHUTDOWN(module) Declares a function for module shutdown. The generated name will be zend_mshutdown_<module> (for example, zend_mshutdown_first_module). Use in conjunction with ZEND_MSHUTDOWN_FUNCTION.
ZEND_RINIT(module) Declares a function for request startup. The generated name will be zend_rinit_<module> (for example, zend_rinit_first_module). Use in conjunction with ZEND_RINIT_FUNCTION.
ZEND_RSHUTDOWN(module) Declares a function for request shutdown. The generated name will be zend_rshutdown_<module> (for example, zend_rshutdown_first_module). Use in conjunction with ZEND_RSHUTDOWN_FUNCTION.
ZEND_MINFO(module) Declares a function for printing module information, used when phpinfo() is called. The generated name will be zend_info_<module> (for example, zend_info_first_module). Use in conjunction with ZEND_MINFO_FUNCTION.
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