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>章 46. Zend API：深入 PHP 内核</TD
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><A
NAME="zend.returning"
>Returning Values</A
></H1
><P
> 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 <CODE
CLASS="envar"
>return_value</CODE
> variable,
which is passed to your functions as argument. The
<CODE
CLASS="envar"
>return_value</CODE
> argument consists of a
<CODE
CLASS="envar"
>zval</CODE
> 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
<TT
CLASS="literal"
>MAKE_STD_ZVAL</TT
> on it. Instead, you can access its
members directly.
</P
><P
> To make returning values from functions easier and to prevent
hassles with accessing the internal structures of the
<CODE
CLASS="envar"
>zval</CODE
> container, a set of predefined macros is
available (as usual). These macros automatically set the
correspondent type and value, as described in
<A
HREF="zend.returning.html#tab.return"
>表 46-14</A
> and <A
HREF="zend.returning.html#tab.retval"
>表 46-15</A
>.
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
The macros in <A
HREF="zend.returning.html#tab.return"
>表 46-14</A
> automatically
<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>return</I
></SPAN
> from your function, those in
<A
HREF="zend.returning.html#tab.retval"
>表 46-15</A
> only <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>set</I
></SPAN
>
the return value; they don't return from your function.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="table"
><A
NAME="tab.return"
></A
><P
><B
>表 46-14. Predefined Macros for Returning Values from a
Function</B
></P
><TABLE
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><COL
WIDTH="1*"
TITLE="col1"><COL
WIDTH="1*"
TITLE="col2"><TBODY
><TR
><TD
>Macro</TD
><TD
>Description</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_RESOURCE(resource)</TT
></TD
><TD
>Returns a resource.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_BOOL(bool)</TT
></TD
><TD
>Returns a Boolean.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_NULL()</TT
></TD
><TD
>Returns nothing (a NULL value).</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_LONG(long)</TT
></TD
><TD
>Returns a long.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_DOUBLE(double)</TT
></TD
><TD
>Returns a double.</TD
></TR
><TR
><TD
> <TT
CLASS="literal"
>RETURN_STRING(string, duplicate)</TT
>
</TD
><TD
> Returns a string. The <CODE
CLASS="envar"
>duplicate</CODE
> flag indicates
whether the string should be duplicated using
<B
CLASS="function"
>estrdup()</B
>.
</TD
></TR
><TR
><TD
> <TT
CLASS="literal"
>RETURN_STRINGL(string, length, duplicate)</TT
>
</TD
><TD
> Returns a string of the specified length; otherwise, behaves
like <TT
CLASS="literal"
>RETURN_STRING</TT
>. This macro is faster
and binary-safe, however.
</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_EMPTY_STRING()</TT
></TD
><TD
>Returns an empty string.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_FALSE</TT
></TD
><TD
>Returns Boolean false.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETURN_TRUE</TT
></TD
><TD
>Returns Boolean true.</TD
></TR
></TBODY
></TABLE
></DIV
><DIV
CLASS="table"
><A
NAME="tab.retval"
></A
><P
><B
>表 46-15. Predefined Macros for Setting the Return Value
of a Function</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL
WIDTH="1*"
TITLE="col1"><COL
WIDTH="1*"
TITLE="col2"><TBODY
><TR
><TD
>Macro</TD
><TD
>Description</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_RESOURCE(resource)</TT
></TD
><TD
>Sets the return value to the specified
resource.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_BOOL(bool)</TT
></TD
><TD
>Sets the return value to the specified
Boolean value.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_NULL</TT
></TD
><TD
>Sets the return value to NULL.</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_LONG(long)</TT
></TD
><TD
> Sets the return value to the specified long.
</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_DOUBLE(double)</TT
></TD
><TD
> Sets the return value to the specified double.
</TD
></TR
><TR
><TD
> <TT
CLASS="literal"
>RETVAL_STRING(string, duplicate)</TT
>
</TD
><TD
> Sets the return value to the specified string and duplicates
it to Zend internal memory if desired (see also
<TT
CLASS="literal"
>RETURN_STRING</TT
>).
</TD
></TR
><TR
><TD
> <TT
CLASS="literal"
>RETVAL_STRINGL(string, length, duplicate)</TT
>
</TD
><TD
> Sets the return value to the specified string and forces the
length to become <CODE
CLASS="envar"
>length</CODE
> (see also
<TT
CLASS="literal"
>RETVAL_STRING</TT
>). This macro is faster and
binary-safe, and should be used whenever the string length is
known.
</TD
></TR
><TR
><TD
> <TT
CLASS="literal"
>RETVAL_EMPTY_STRING</TT
>
</TD
><TD
> Sets the return value to an empty string.
</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_FALSE</TT
></TD
><TD
> Sets the return value to Boolean false.
</TD
></TR
><TR
><TD
><TT
CLASS="literal"
>RETVAL_TRUE</TT
></TD
><TD
> Sets the return value to Boolean true.
</TD
></TR
></TBODY
></TABLE
></DIV
><P
> Complex types such as arrays and objects can be returned by using
<A
HREF="zend-api.array-init.html"
><B
CLASS="function"
>array_init()</B
></A
> and
<A
HREF="zend-api.object-init.html"
><B
CLASS="function"
>object_init()</B
></A
>, as well as the corresponding hash
functions on <CODE
CLASS="envar"
>return_value</CODE
>. Since these types cannot
be constructed of trivial information, there are no predefined
macros for them.
</P
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