Programming PHP

using SEPARATE_ZVAL( ), initializes the return_value to be an array, and fills in the
array. The big trick here is the zval_add_ref( ) call. This function increments the reference
count on the zval container. Therefore, instead of making n copies of the container,
one for each element, we have only one copy, with a reference count of n+1.
Remember, is_ref is still 0 here.
Here’s how this function could be used in a PHP script:
This would result in a two-dimensional array that looks like this:
$arr[0][0] = 1 $arr[0][1] = 2 $arr[0][2] = 3
$arr[1][0] = 1 $arr[1][1] = 2 $arr[1][2] = 3
$arr[2][0] = 1 $arr[2][1] = 2 $arr[2][2] = 3
Internally, a copy-on-write of the appropriate container is done if any of these array
elements are changed. The engine knows to do a copy-on-write when it sees something
being assigned to a zval container whose reference count is greater than 1 and
whose is_ref is 0. We could have written our function to do a MAKE_STD_ZVAL( ) for
each element in our array, but it would have been about twice as slow as simply
incrementing the reference count and letting a copy-on-write make a separate copy
later if necessary.
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, for example, uses the CGI SAPI layer. There
is also a Java SAPI module. You can check which SAPI module you are running
under by including SAPI.h and then checking sapi_module.name:
#include
/* 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)
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