Data Values

As with type, the value of zvals can be inspected using a triplet of macros. These macros also begin with Z_, and optionally end with _P or _PP depending on their degree of indirection.

For the simple scalar types, Boolean, long, and double, the macros are short and consistent: BVAL, LVAL, and DVAL.

void display_values(zval boolzv, zval *longpzv, zval **doubleppzv) { if (Z_TYPE(boolzv) == IS_BOOL) { php_printf("The value of the boolean is: %s ", Z_BVAL(boolzv) ? "true" : "false"); } if (Z_TYPE_P(longpzv) == IS_LONG) { php_printf("The value of the long is: %ld ", Z_LVAL_P(longpzv)); } if (Z_TYPE_PP(doubleppzv) == IS_DOUBLE) { php_printf("The value of the double is: %f ", Z_DVAL_PP(doubleppzv)); } }

String variables, because they contain two attributes, have a pair of macro triplets representing the char* (STRVAL) and int (STRLEN) elements:

void display_string(zval *zstr) { if (Z_TYPE_P(zstr) != IS_STRING) { php_printf("The wrong datatype was passed! "); return; } PHPWRITE(Z_STRVAL_P(zstr), Z_STRLEN_P(zstr)); }

The array data type is stored internally as a HashTable* that can be accessed using the ARRVAL triplet: Z_ARRVAL(zv), Z_ARRVAL_P(pzv), Z_ARRVAL_PP(ppzv). When looking through old code in the PHP core and PECL modules, you might encounter the HASH_OF() macro, which expects a zval*. This macro is generally the equivalent of the Z_ARRVAL_P() macro; however, its use is deprecated and should not be used with new code.

Objects represent complex internal structures and have a number of access macros: OBJ_HANDLE, which returns the handle identifier, OBJ_HT for the handler table, OBJCE for the class definition, OBJPROP for the property HashTable, and OBJ_HANDLER for manipulating a specific handler method in the OBJ_HT table. Don't worry about the meaning of these various object macros just yet; they'll be covered in detail in Chapter 10, "PHP4 Objects," and Chapter 11, "PHP5 Objects."

Within a zval, a resource data type is stored as a simple integer that can be accessed with the RESVAL tripplet. This integer is passed on to the zend_fetch_resource() function which looks up the registered resource from its numeric identifier. The resource data type will be covered in depth in Chapter 9.