Extension Writing Part II: Parameters, Arrays, and ZVALs [continued]

系统管理员 2022-08-06 17:00 203阅读 0赞

http://devzone.zend.com/318/extension-writing-part-ii-parameters-arrays-and-zvals-continued/\#Heading9

[Introduction][]  
. [Accepting Values][]  
. [The ZVAL][]  
. [Creating ZVALs][]  
. [Arrays][]  
. [Symbol Tables as Arrays][]  
. [Reference Counting][]  
[Copies versus References][]  
[Sanity Check][]  
[What’s Next?][What_s Next]

### Copies versus References ###

There are two ways to reference a `zval`. The first, demonstrated above, is known as copy-on-write referencing. The second form, full referencing, is what a userspace script writer is more familiar with in relationship to the word “reference” and occurs with userspace code like: `$a = &$b;`.

In a `zval`, these two types are differentiated with the member value `is_ref,`which will be 0 for copy references, and non-zero for full references. Note that it’s not possible for a `zval` to be both a copy style reference and a full reference. So if a variable starts off being `is_ref`, and is then assigned to a new variable as a copy, a full copy must be performed. Consider the following userspace code:

In this block of code, a `zval` is created for `$a`, initially with `is_ref` set to 0 and `refcount__gc` set to 1. When `$a` is referenced to `$b`, `is_ref` gets changed to 1, and `refcount__gc` increases to 2. When a copy is made into `$c`, the Zend Engine can’t just simply increase the `refcount__gc` to 3 since `$c` would then be seen as a full reference to `$a`. Turning off `is_ref` wouldn’t work either since `$b`would now be seen as a copy of `$a`, rather than a reference. So at this point a new `zval` is allocated, and the value of the original is copied into it with`zval_copy_ctor()`. The original `zval` is left with `is_ref==1` and `refcount__gc==2`, while the new `zval` has `is_ref=0` and `refcount__gc=1`. Now look at that same code block done in a slightly different order:

The end result is the same, with `$b` being a full reference to `$a`, and `$c`being a copy of `$a`. This time, however, the internal actions are slightly different. As before, a new `zval` is created for `$a` at the beginning with`is_ref==0` and `refcount__gc=1`. The `$c = $a;` statement then assigns the same `zval`to the `$c` variable while incrementing the `refcount__gc` to 2, and leaving `is_ref`as 0. When the Zend Engine encounters `$b = &$a;` it wants to just set `is_ref`to 1, but of course can’t since that would impact `$c`. Instead it creates a new `zval` and copies the contents of the original into it with`zval_copy_ctor()`, then decrements `refcount__gc` in the original `zval` to signify that `$a` is no longer using that `zval`. Instead, it sets the new `zval`‘s `is_ref`to 1, its `refcount__gc` to 2, and updates the `$a` and `$b` variables to refer to it.

### Sanity Check ###

As before, the complete code listing for our three primary files is provided whole and intact below:

### config.m4 ###

### php\_hello.h ###

### hello.c ###

<table style="border:1px solid rgb(230,230,230); outline:0px; font-size:14px; vertical-align:baseline; margin:0px 0px 1.2em; padding:0px; border-collapse:collapse; border-spacing:0px; width:541px; background:transparent"> 
 <tbody style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; background:transparent"> 
 <tr style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; background:transparent"> 
 <td style="border:1px solid rgb(230,230,230); outline:0px; font-size:14px; vertical-align:baseline; margin:0px; padding:6px 0px 3px 10px; background:transparent"> <code style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; background:transparent"> #ifdef HAVE_CONFIG_H #include "config.h" #endif</code> #include "php.h" #include "php_ini.h" #include "php_hello.h" ZEND_DECLARE_MODULE_GLOBALS(hello) static zend_function_entry hello_functions[] = { &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_world, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_long, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_double, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_bool, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_null, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_greetme, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_add, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_dump, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_array, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_array_strings, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_array_walk, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_array_value, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_get_global_var, NULL) &nbsp;&nbsp;&nbsp;&nbsp;PHP_FE(hello_set_local_var, NULL) &nbsp;&nbsp;&nbsp;&nbsp;{NULL, NULL, NULL} }; zend_module_entry hello_module_entry = { #if ZEND_MODULE_API_NO &gt;= 20010901 &nbsp;&nbsp;&nbsp;&nbsp;STANDARD_MODULE_HEADER, #endif &nbsp;&nbsp;&nbsp;&nbsp;PHP_HELLO_WORLD_EXTNAME, &nbsp;&nbsp;&nbsp;&nbsp;hello_functions, &nbsp;&nbsp;&nbsp;&nbsp;PHP_MINIT(hello), &nbsp;&nbsp;&nbsp;&nbsp;PHP_MSHUTDOWN(hello), &nbsp;&nbsp;&nbsp;&nbsp;PHP_RINIT(hello), &nbsp;&nbsp;&nbsp;&nbsp;NULL, &nbsp;&nbsp;&nbsp;&nbsp;NULL, #if ZEND_MODULE_API_NO &gt;= 20010901 &nbsp;&nbsp;&nbsp;&nbsp;PHP_HELLO_WORLD_VERSION, #endif &nbsp;&nbsp;&nbsp;&nbsp;STANDARD_MODULE_PROPERTIES }; #ifdef COMPILE_DL_HELLO &nbsp;&nbsp;&nbsp;&nbsp;ZEND_GET_MODULE(hello) #endif PHP_INI_BEGIN() &nbsp;&nbsp;&nbsp;&nbsp;PHP_INI_ENTRY("hello.greeting", "Hello World", PHP_INI_ALL, NULL) &nbsp;&nbsp;&nbsp;&nbsp;STD_PHP_INI_ENTRY("hello.direction", "1", PHP_INI_ALL, OnUpdateBool, direction, zend_hello_globals, hello_globals) PHP_INI_END() static void php_hello_init_globals(zend_hello_globals *hello_globals) { &nbsp;&nbsp;&nbsp;&nbsp;hello_globals-&gt;direction = 1; } PHP_RINIT_FUNCTION(hello) { &nbsp;&nbsp;&nbsp;&nbsp;HELLO_G(counter) = 0; &nbsp;&nbsp;&nbsp;&nbsp;return SUCCESS; } PHP_MINIT_FUNCTION(hello) { &nbsp;&nbsp;&nbsp;&nbsp;ZEND_INIT_MODULE_GLOBALS(hello, php_hello_init_globals, NULL); &nbsp;&nbsp;&nbsp;&nbsp;REGISTER_INI_ENTRIES(); &nbsp;&nbsp;&nbsp;&nbsp;return SUCCESS; } PHP_MSHUTDOWN_FUNCTION(hello) { &nbsp;&nbsp;&nbsp;&nbsp;UNREGISTER_INI_ENTRIES(); &nbsp;&nbsp;&nbsp;&nbsp;return SUCCESS; } PHP_FUNCTION(hello_world) { &nbsp;&nbsp;&nbsp;&nbsp;RETURN_STRING("Hello World", 1); } PHP_FUNCTION(hello_long) { &nbsp;&nbsp;&nbsp;&nbsp;if (HELLO_G(direction)) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;HELLO_G(counter)++; &nbsp;&nbsp;&nbsp;&nbsp;} else { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;HELLO_G(counter)--; &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;RETURN_LONG(HELLO_G(counter)); } PHP_FUNCTION(hello_double) { &nbsp;&nbsp;&nbsp;&nbsp;RETURN_DOUBLE(3.1415926535); } PHP_FUNCTION(hello_bool) { &nbsp;&nbsp;&nbsp;&nbsp;RETURN_BOOL(1); } PHP_FUNCTION(hello_null) { &nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); } PHP_FUNCTION(hello_greetme) { &nbsp;&nbsp;&nbsp;&nbsp;zval *zname; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "z", &amp;zname) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;convert_to_string(zname); &nbsp;&nbsp;&nbsp;&nbsp;php_printf("Hello "); &nbsp;&nbsp;&nbsp;&nbsp;PHPWRITE(Z_STRVAL_P(zname), Z_STRLEN_P(zname)); &nbsp;&nbsp;&nbsp;&nbsp;php_printf(" "); &nbsp;&nbsp;&nbsp;&nbsp;RETURN_TRUE; } PHP_FUNCTION(hello_add) { &nbsp;&nbsp;&nbsp;&nbsp;long a; &nbsp;&nbsp;&nbsp;&nbsp;double b; &nbsp;&nbsp;&nbsp;&nbsp;zend_bool return_long = 0; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ld|b", &amp;a, &amp;b, &amp;return_long) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;if (return_long) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_LONG(a + b); &nbsp;&nbsp;&nbsp;&nbsp;} else { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_DOUBLE(a + b); &nbsp;&nbsp;&nbsp;&nbsp;} } PHP_FUNCTION(hello_dump) { &nbsp;&nbsp;&nbsp;&nbsp;zval *uservar; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "z", &amp;uservar) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;switch (Z_TYPE_P(uservar)) { &nbsp;&nbsp;&nbsp;&nbsp;case IS_NULL: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("NULL "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_BOOL: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Boolean: %s ", Z_LVAL_P(uservar) ? "TRUE" : "FALSE"); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_LONG: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Long: %ld ", Z_LVAL_P(uservar)); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_DOUBLE: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Double: %f ", Z_DVAL_P(uservar)); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_STRING: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("String: "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PHPWRITE(Z_STRVAL_P(uservar), Z_STRLEN_P(uservar)); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf(" "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_RESOURCE: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Resource "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_ARRAY: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Array "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_OBJECT: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Object "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;default: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("Unknown "); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;RETURN_TRUE; } PHP_FUNCTION(hello_array) { &nbsp;&nbsp;&nbsp;&nbsp;char *mystr; &nbsp;&nbsp;&nbsp;&nbsp;zval *mysubarray; &nbsp;&nbsp;&nbsp;&nbsp;array_init(return_value); &nbsp;&nbsp;&nbsp;&nbsp;add_index_long(return_value, 42, 123); &nbsp;&nbsp;&nbsp;&nbsp;add_next_index_string(return_value, "I should now be found at index 43", 1); &nbsp;&nbsp;&nbsp;&nbsp;add_next_index_stringl(return_value, "I'm at 44!", 10, 1); &nbsp;&nbsp;&nbsp;&nbsp;mystr = estrdup("Forty Five"); &nbsp;&nbsp;&nbsp;&nbsp;add_next_index_string(return_value, mystr, 0); &nbsp;&nbsp;&nbsp;&nbsp;add_assoc_double(return_value, "pi", 3.1415926535); &nbsp;&nbsp;&nbsp;&nbsp;ALLOC_INIT_ZVAL(mysubarray); &nbsp;&nbsp;&nbsp;&nbsp;array_init(mysubarray); &nbsp;&nbsp;&nbsp;&nbsp;add_next_index_string(mysubarray, "hello", 1); &nbsp;&nbsp;&nbsp;&nbsp;php_printf("mysubarray-&gt;refcount__gc = %d ", mysubarray-&gt;refcount__gc); &nbsp;&nbsp;&nbsp;&nbsp;mysubarray-&gt;refcount__gc = 2; &nbsp;&nbsp;&nbsp;&nbsp;php_printf("mysubarray-&gt;refcount__gc = %d ", mysubarray-&gt;refcount__gc); &nbsp;&nbsp;&nbsp;&nbsp;add_assoc_zval(return_value, "subarray", mysubarray); &nbsp;&nbsp;&nbsp;&nbsp;php_printf("mysubarray-&gt;refcount__gc = %d ", mysubarray-&gt;refcount__gc); } PHP_FUNCTION(hello_array_strings) { &nbsp;&nbsp;&nbsp;&nbsp;zval *arr, **data; &nbsp;&nbsp;&nbsp;&nbsp;HashTable *arr_hash; &nbsp;&nbsp;&nbsp;&nbsp;HashPosition pointer; &nbsp;&nbsp;&nbsp;&nbsp;int array_count; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &amp;arr) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;arr_hash = Z_ARRVAL_P(arr); &nbsp;&nbsp;&nbsp;&nbsp;array_count = zend_hash_num_elements(arr_hash); &nbsp;&nbsp;&nbsp;&nbsp;php_printf("The array passed contains %d elements ", array_count); &nbsp;&nbsp;&nbsp;&nbsp;for(zend_hash_internal_pointer_reset_ex(arr_hash, &amp;pointer); zend_hash_get_current_data_ex(arr_hash, (void**) &amp;data, &amp;pointer) == SUCCESS; zend_hash_move_forward_ex(arr_hash, &amp;pointer)) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;zval temp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;char *key; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int key_len; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;long index; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (zend_hash_get_current_key_ex(arr_hash, &amp;key, &amp;key_len, &amp;index, 0, &amp;pointer) == HASH_KEY_IS_STRING) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PHPWRITE(key, key_len); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;} else { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf("%ld", index); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf(" =&gt; "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;temp = **data; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;zval_copy_ctor(&amp;temp); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;convert_to_string(&amp;temp); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PHPWRITE(Z_STRVAL(temp), Z_STRLEN(temp)); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_printf(" "); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;zval_dtor(&amp;temp); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;RETURN_TRUE; } static int php_hello_array_walk(zval **element TSRMLS_DC) { &nbsp;&nbsp;&nbsp;&nbsp;zval temp; &nbsp;&nbsp;&nbsp;&nbsp;temp = **element; &nbsp;&nbsp;&nbsp;&nbsp;zval_copy_ctor(&amp;temp); &nbsp;&nbsp;&nbsp;&nbsp;convert_to_string(&amp;temp); &nbsp;&nbsp;&nbsp;&nbsp;PHPWRITE(Z_STRVAL(temp), Z_STRLEN(temp)); &nbsp;&nbsp;&nbsp;&nbsp;php_printf(" "); &nbsp;&nbsp;&nbsp;&nbsp;zval_dtor(&amp;temp); &nbsp;&nbsp;&nbsp;&nbsp;return ZEND_HASH_APPLY_KEEP; } static int php_hello_array_walk_arg(zval **element, char *greeting TSRMLS_DC) { &nbsp;&nbsp;&nbsp;&nbsp;php_printf("%s", greeting); &nbsp;&nbsp;&nbsp;&nbsp;php_hello_array_walk(element TSRMLS_CC); &nbsp;&nbsp;&nbsp;&nbsp;return ZEND_HASH_APPLY_KEEP; } static int php_hello_array_walk_args(zval **element, int num_args, va_list args, zend_hash_key *hash_key) { &nbsp;&nbsp;&nbsp;&nbsp;char *prefix = va_arg(args, char*); &nbsp;&nbsp;&nbsp;&nbsp;char *suffix = va_arg(args, char*); &nbsp;&nbsp;&nbsp;&nbsp;TSRMLS_FETCH(); &nbsp;&nbsp;&nbsp;&nbsp;php_printf("%s", prefix); &nbsp;&nbsp;&nbsp;&nbsp;php_hello_array_walk(element TSRMLS_CC); &nbsp;&nbsp;&nbsp;&nbsp;php_printf("%s ", suffix); &nbsp;&nbsp;&nbsp;&nbsp;return ZEND_HASH_APPLY_KEEP; } PHP_FUNCTION(hello_array_walk) { &nbsp;&nbsp;&nbsp;&nbsp;zval *zarray; &nbsp;&nbsp;&nbsp;&nbsp;int print_newline = 1; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &amp;zarray) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;zend_hash_apply(Z_ARRVAL_P(zarray), (apply_func_t)php_hello_array_walk TSRMLS_CC); &nbsp;&nbsp;&nbsp;&nbsp;zend_hash_internal_pointer_reset(Z_ARRVAL_P(zarray)); &nbsp;&nbsp;&nbsp;&nbsp;zend_hash_apply_with_argument(Z_ARRVAL_P(zarray), (apply_func_arg_t)php_hello_array_walk_arg, "Hello " TSRMLS_CC); &nbsp;&nbsp;&nbsp;&nbsp;zend_hash_apply_with_arguments(Z_ARRVAL_P(zarray), (apply_func_args_t)php_hello_array_walk_args, 2, "Hello ", "Welcome to my extension!"); &nbsp;&nbsp;&nbsp;&nbsp;RETURN_TRUE; } PHP_FUNCTION(hello_array_value) { &nbsp;&nbsp;&nbsp;&nbsp;zval *zarray, *zoffset, **zvalue; &nbsp;&nbsp;&nbsp;&nbsp;long index = 0; &nbsp;&nbsp;&nbsp;&nbsp;char *key = NULL; &nbsp;&nbsp;&nbsp;&nbsp;int key_len = 0; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "az", &amp;zarray, &amp;zoffset) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;switch (Z_TYPE_P(zoffset)) { &nbsp;&nbsp;&nbsp;&nbsp;case IS_NULL: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;index = 0; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_DOUBLE: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;index = (long)Z_DVAL_P(zoffset); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_BOOL: &nbsp;&nbsp;&nbsp;&nbsp;case IS_LONG: &nbsp;&nbsp;&nbsp;&nbsp;case IS_RESOURCE: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;index = Z_LVAL_P(zoffset); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_STRING: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key = Z_STRVAL_P(zoffset); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key_len = Z_STRLEN_P(zoffset); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_ARRAY: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key = "Array"; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key_len =&nbsp;<a style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; color:rgb(64,129,175); background:transparent" rel="nofollow">sizeof</a>("Array") - 1; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;case IS_OBJECT: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key = "Object"; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key_len =&nbsp;<a style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; color:rgb(64,129,175); background:transparent" rel="nofollow">sizeof</a>("Object") - 1; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break; &nbsp;&nbsp;&nbsp;&nbsp;default: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key = "Unknown"; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;key_len =&nbsp;<a style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; color:rgb(64,129,175); background:transparent" rel="nofollow">sizeof</a>("Unknown") - 1; &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;if (key &amp;&amp; zend_hash_find(Z_ARRVAL_P(zarray), key, key_len + 1, (void**)&amp;zvalue) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_error_docref(NULL TSRMLS_CC, E_NOTICE, "Undefined index: %s", key); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} else if (!key &amp;&amp; zend_hash_index_find(Z_ARRVAL_P(zarray), index, (void**)&amp;zvalue) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_error_docref(NULL TSRMLS_CC, E_NOTICE, "Undefined index: %ld", index); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;*return_value = **zvalue; &nbsp;&nbsp;&nbsp;&nbsp;zval_copy_ctor(return_value); } PHP_FUNCTION(hello_get_global_var) { &nbsp;&nbsp;&nbsp;&nbsp;char *varname; &nbsp;&nbsp;&nbsp;&nbsp;int varname_len; &nbsp;&nbsp;&nbsp;&nbsp;zval **varvalue; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &amp;varname, &amp;varname_len) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;if (zend_hash_find(&amp;EG(symbol_table), varname, varname_len + 1, (void**)&amp;varvalue) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;php_error_docref(NULL TSRMLS_CC, E_NOTICE, "Undefined variable: %s", varname); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;*return_value = **varvalue; &nbsp;&nbsp;&nbsp;&nbsp;zval_copy_ctor(return_value); } PHP_FUNCTION(hello_set_local_var) { &nbsp;&nbsp;&nbsp;&nbsp;zval *newvar; &nbsp;&nbsp;&nbsp;&nbsp;char *varname; &nbsp;&nbsp;&nbsp;&nbsp;int varname_len; &nbsp;&nbsp;&nbsp;&nbsp;zval *value; &nbsp;&nbsp;&nbsp;&nbsp;if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sz", &amp;varname, &amp;varname_len, &amp;value) == FAILURE) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RETURN_NULL(); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;ALLOC_INIT_ZVAL(newvar); &nbsp;&nbsp;&nbsp;&nbsp;*newvar = *value; &nbsp;&nbsp;&nbsp;&nbsp;zval_copy_ctor(newvar); &nbsp;&nbsp;&nbsp;&nbsp;zend_hash_add(EG(active_symbol_table), varname, varname_len + 1, &amp;newvar,&nbsp;<a style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; color:rgb(64,129,175); background:transparent" rel="nofollow">sizeof</a>(zval*), NULL); <code style="border:0px; outline:0px; vertical-align:baseline; margin:0px; padding:0px; background:transparent">&nbsp;&nbsp;&nbsp;&nbsp;RETURN_TRUE; } </code> </td> 
 </tr> 
 </tbody> 
</table>

### What’s Next? ###

In this tutorial, Part Two of the Extension Writing series, you learned how to accept  
function parameters, you created and used arrays, and, most importantly, you took a  
look at the inner workings of the `zval`. In [Part Three][], you’ll take a look  
at the `resource` data type and start working with more complex data structures.

[Introduction]: http://devzone.zend.com/article/1022#Heading1
[Accepting Values]: http://devzone.zend.com/article/1022#Heading2
[The ZVAL]: http://devzone.zend.com/article/1022#Heading3
[Creating ZVALs]: http://devzone.zend.com/article/1022#Heading4
[Arrays]: http://devzone.zend.com/article/1022#Heading5
[Symbol Tables as Arrays]: http://devzone.zend.com/article/1022#Heading6
[Reference Counting]: http://devzone.zend.com/article/1022#Heading7
[Copies versus References]: http://devzone.zend.com/318/extension-writing-part-ii-parameters-arrays-and-zvals-continued/#Heading8
[Sanity Check]: http://devzone.zend.com/318/extension-writing-part-ii-parameters-arrays-and-zvals-continued/#Heading9
[What_s Next]: http://devzone.zend.com/318/extension-writing-part-ii-parameters-arrays-and-zvals-continued/#Heading10
[Part Three]: http://devzone.zend.com/article/1024