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# 35. 장. 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 표 35-1 and 표 35-2.

> 참고: The macros in 표 35-1 automatically return from your function, those in 표 35-2 only set the return value; they don't return from your function.

표 35-1. 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.

표 35-2. 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.

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