Capitolo 37. Returning Values
Returning values from your functions to PHP was described briefly
in an earlier section; this section gives the details. Return
values are passed via the return_value variable,
which is passed to your functions as argument. The
return_value argument consists of a
zval container (see the earlier discussion of the
call interface) that you can freely modify. The container itself is
already allocated, so you don't have to run
MAKE_STD_ZVAL on it. Instead, you can access its
members directly.
To make returning values from functions easier and to prevent
hassles with accessing the internal structures of the
zval container, a set of predefined macros is
available (as usual). These macros automatically set the
correspondent type and value, as described in
Tabella 37-1 and Tabella 37-2.
Nota:
The macros in Tabella 37-1 automatically
return from your function, those in
Tabella 37-2 only set
the return value; they don't return from your function.
Tabella 37-1. Predefined Macros for Returning Values from a
Function
| Macro | Description |
| RETURN_RESOURCE(resource) | Returns a resource. |
| RETURN_BOOL(bool) | Returns a Boolean. |
| RETURN_NULL() | Returns nothing (a NULL value). |
| RETURN_LONG(long) | Returns a long. |
| RETURN_DOUBLE(double) | Returns a double. |
|
RETURN_STRING(string, duplicate)
|
Returns a string. The duplicate flag indicates
whether the string should be duplicated using
estrdup().
|
|
RETURN_STRINGL(string, length, duplicate)
|
Returns a string of the specified length; otherwise, behaves
like RETURN_STRING. This macro is faster
and binary-safe, however.
|
| RETURN_EMPTY_STRING() | Returns an empty string. |
| RETURN_FALSE | Returns Boolean false. |
| RETURN_TRUE | Returns Boolean true. |
Tabella 37-2. Predefined Macros for Setting the Return Value
of a Function
| Macro | Description |
| RETVAL_RESOURCE(resource) | Sets the return value to the specified
resource. |
| RETVAL_BOOL(bool) | Sets the return value to the specified
Boolean value. |
| RETVAL_NULL | Sets the return value to NULL. |
| RETVAL_LONG(long) |
Sets the return value to the specified long.
|
| RETVAL_DOUBLE(double) |
Sets the return value to the specified double.
|
|
RETVAL_STRING(string, duplicate)
|
Sets the return value to the specified string and duplicates
it to Zend internal memory if desired (see also
RETURN_STRING).
|
|
RETVAL_STRINGL(string, length, duplicate)
|
Sets the return value to the specified string and forces the
length to become length (see also
RETVAL_STRING). This macro is faster and
binary-safe, and should be used whenever the string length is
known.
|
|
RETVAL_EMPTY_STRING
|
Sets the return value to an empty string.
|
| RETVAL_FALSE |
Sets the return value to Boolean false.
|
| RETVAL_TRUE |
Sets the return value to Boolean true.
|
Complex types such as arrays and objects can be returned by using
array_init() and
object_init(), as well as the corresponding hash
functions on return_value. Since these types cannot
be constructed of trivial information, there are no predefined
macros for them.
Duplicating Variable Contents: The Copy Constructor
