php/README.EXTENSIONS

Between PHP 4.0.6 and 4.1.0, the Zend module struct changed in a way
that broke both source and binary compatibility.  If you are
maintaining a third party extension, here's how to update it:

If this was your old module entry:

zend_module_entry foo_module_entry = {
    "foo",                /* extension name */
    foo_functions,        /* extension function list */
    NULL,                 /* extension-wide startup function */
    NULL,                 /* extension-wide shutdown function */
    PHP_RINIT(foo),       /* per-request startup function */
    PHP_RSHUTDOWN(foo),   /* per-request shutdown function */
    PHP_MINFO(foo),       /* information function */
    STANDARD_MODULE_PROPERTIES
};

Here's how it should look if you want your code to build with PHP
4.1.0 and up:

zend_module_entry foo_module_entry = {
#if ZEND_MODULE_API_NO >= 20010901
    STANDARD_MODULE_HEADER,
#endif
    "foo",                /* extension name */
    foo_functions,        /* extension function list */
    NULL,                 /* extension-wide startup function */
    NULL,                 /* extension-wide shutdown function */
    PHP_RINIT(foo),       /* per-request startup function */
    PHP_RSHUTDOWN(foo),   /* per-request shutdown function */
    PHP_MINFO(foo),       /* information function */
#if ZEND_MODULE_API_NO >= 20010901
    FOO_VERSION,          /* extension version number (string) */
#endif
    STANDARD_MODULE_PROPERTIES
};

If you don't care about source compatibility with earlier PHP releases
than 4.1.0, you can drop the #if/#endif lines.